JAVA-12097: renamed algorithms-module to algorithms-modules

2022-05-20 22:07:32 +05:30
parent 3b028d36d0
commit a2afe2eed0
324 changed files with 31 additions and 20 deletions
--- a/algorithms-modules/algorithms-miscellaneous-6/README.md
+++ b/algorithms-modules/algorithms-miscellaneous-6/README.md
@@ -0,0 +1,13 @@
+### Relevant Articles:
+
+- [Boruvka’s Algorithm for Minimum Spanning Trees in Java](https://www.baeldung.com/java-boruvka-algorithm)
+- [Gradient Descent in Java](https://www.baeldung.com/java-gradient-descent)
+- [Kruskal’s Algorithm for Spanning Trees with a Java Implementation](https://www.baeldung.com/java-spanning-trees-kruskal)
+- [Balanced Brackets Algorithm in Java](https://www.baeldung.com/java-balanced-brackets-algorithm)
+- [Efficiently Merge Sorted Java Sequences](https://www.baeldung.com/java-merge-sorted-sequences)
+- [Introduction to Greedy Algorithms with Java](https://www.baeldung.com/java-greedy-algorithms)
+- [The Caesar Cipher in Java](https://www.baeldung.com/java-caesar-cipher)
+- [Implementing a 2048 Solver in Java](https://www.baeldung.com/2048-java-solver)
+- [Finding Top K Elements in a Java Array](https://www.baeldung.com/java-array-top-elements)
+- [Reversing a Linked List in Java](https://www.baeldung.com/java-reverse-linked-list)
+- More articles: [[<-- prev]](/algorithms-miscellaneous-5)
--- a/algorithms-modules/algorithms-miscellaneous-6/pom.xml
+++ b/algorithms-modules/algorithms-miscellaneous-6/pom.xml
@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>algorithms-miscellaneous-6</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>algorithms-miscellaneous-6</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>algorithms-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>${lombok.version}</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-math3</artifactId>
+            <version>${commons-math3.version}</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <commons-math3.version>3.6.1</commons-math3.version>
+    </properties>
+
+</project>
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/balancedbrackets/BalancedBracketsUsingDeque.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/balancedbrackets/BalancedBracketsUsingDeque.java
@@ -0,0 +1,36 @@
+package com.baeldung.algorithms.balancedbrackets;
+
+import java.util.Deque;
+import java.util.LinkedList;
+
+public class BalancedBracketsUsingDeque {
+
+    public boolean isBalanced(String str) {
+        if (null == str || ((str.length() % 2) != 0)) {
+            return false;
+        } else {
+            char[] ch = str.toCharArray();
+            for (char c : ch) {
+                if (!(c == '{' || c == '[' || c == '(' || c == '}' || c == ']' || c == ')')) {
+                    return false;
+                }
+
+            }
+        }
+
+        Deque<Character> deque = new LinkedList<>();
+        for (char ch : str.toCharArray()) {
+            if (ch == '{' || ch == '[' || ch == '(') {
+                deque.addFirst(ch);
+            } else {
+                if (!deque.isEmpty() && ((deque.peekFirst() == '{' && ch == '}') || (deque.peekFirst() == '[' && ch == ']') || (deque.peekFirst() == '(' && ch == ')'))) {
+                    deque.removeFirst();
+                } else {
+                    return false;
+                }
+            }
+        }
+
+        return deque.isEmpty();
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/balancedbrackets/BalancedBracketsUsingString.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/balancedbrackets/BalancedBracketsUsingString.java
@@ -0,0 +1,27 @@
+package com.baeldung.algorithms.balancedbrackets;
+
+public class BalancedBracketsUsingString {
+
+    public boolean isBalanced(String str) {
+        if (null == str || ((str.length() % 2) != 0)) {
+            return false;
+        } else {
+            char[] ch = str.toCharArray();
+            for (char c : ch) {
+                if (!(c == '{' || c == '[' || c == '(' || c == '}' || c == ']' || c == ')')) {
+                    return false;
+                }
+
+            }
+        }
+
+        while (str.contains("()") || str.contains("[]") || str.contains("{}")) {
+            str = str.replaceAll("\\(\\)", "")
+                .replaceAll("\\[\\]", "")
+                .replaceAll("\\{\\}", "");
+        }
+        return (str.length() == 0);
+
+    }
+
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/boruvka/BoruvkaMST.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/boruvka/BoruvkaMST.java
@@ -0,0 +1,84 @@
+package com.baeldung.algorithms.boruvka;
+
+import com.google.common.graph.EndpointPair;
+import com.google.common.graph.MutableValueGraph;
+import com.google.common.graph.ValueGraphBuilder;
+
+public class BoruvkaMST {
+
+    private static MutableValueGraph<Integer, Integer> mst = ValueGraphBuilder.undirected()
+        .build();
+    private static int totalWeight;
+
+    public BoruvkaMST(MutableValueGraph<Integer, Integer> graph) {
+
+        int size = graph.nodes().size();
+
+        UnionFind uf = new UnionFind(size);
+
+        // repeat at most log N times or until we have N-1 edges
+        for (int t = 1; t < size && mst.edges().size() < size - 1; t = t + t) {
+            
+            EndpointPair<Integer>[] closestEdgeArray = new EndpointPair[size];
+
+            // foreach tree in graph, find closest edge
+            for (EndpointPair<Integer> edge : graph.edges()) {
+                int u = edge.nodeU();
+                int v = edge.nodeV();
+                int uParent = uf.find(u);
+                int vParent = uf.find(v);
+                if (uParent == vParent) {
+                    continue; // same tree
+                }
+
+                int weight = graph.edgeValueOrDefault(u, v, 0);
+
+                if (closestEdgeArray[uParent] == null) {
+                    closestEdgeArray[uParent] = edge;
+                }
+                if (closestEdgeArray[vParent] == null) {
+                    closestEdgeArray[vParent] = edge;
+                }
+
+                int uParentWeight = graph.edgeValueOrDefault(closestEdgeArray[uParent].nodeU(), closestEdgeArray[uParent].nodeV(), 0);
+                int vParentWeight = graph.edgeValueOrDefault(closestEdgeArray[vParent].nodeU(), closestEdgeArray[vParent].nodeV(), 0);
+
+                if (weight < uParentWeight) {
+                    closestEdgeArray[uParent] = edge;
+                }
+                if (weight < vParentWeight) {
+                    closestEdgeArray[vParent] = edge;
+                }
+            }
+
+            // add newly discovered edges to MST
+            for (int i = 0; i < size; i++) {
+                EndpointPair<Integer> edge = closestEdgeArray[i];
+                if (edge != null) {
+                    int u = edge.nodeU();
+                    int v = edge.nodeV();
+                    int weight = graph.edgeValueOrDefault(u, v, 0);
+                    // don't add the same edge twice
+                    if (uf.find(u) != uf.find(v)) {
+                        mst.putEdgeValue(u, v, weight);
+                        totalWeight += weight;
+                        uf.union(u, v);
+                    }
+                }
+            }
+        }
+    }
+
+    public MutableValueGraph<Integer, Integer> getMST() {
+        return mst;
+    }
+
+    public int getTotalWeight() {
+        return totalWeight;
+    }
+
+    public String toString() {
+        return "MST: " + mst.toString() + " | Total Weight: " + totalWeight;
+    }
+
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/boruvka/UnionFind.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/boruvka/UnionFind.java
@@ -0,0 +1,39 @@
+package com.baeldung.algorithms.boruvka;
+
+public class UnionFind {
+    private int[] parents;
+    private int[] ranks;
+
+    public UnionFind(int n) {
+        parents = new int[n];
+        ranks = new int[n];
+        for (int i = 0; i < n; i++) {
+            parents[i] = i;
+            ranks[i] = 0;
+        }
+    }
+
+    public int find(int u) {
+        while (u != parents[u]) {
+            u = parents[u];
+        }
+        return u;
+    }
+
+    public void union(int u, int v) {
+        int uParent = find(u);
+        int vParent = find(v);
+        if (uParent == vParent) {
+            return;
+        }
+
+        if (ranks[uParent] < ranks[vParent]) {
+            parents[uParent] = vParent;
+        } else if (ranks[uParent] > ranks[vParent]) {
+            parents[vParent] = uParent;
+        } else {
+            parents[vParent] = uParent;
+            ranks[uParent]++;
+        }
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/caesarcipher/CaesarCipher.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/caesarcipher/CaesarCipher.java
@@ -0,0 +1,88 @@
+package com.baeldung.algorithms.caesarcipher;
+
+import org.apache.commons.math3.stat.inference.ChiSquareTest;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Arrays;
+import java.util.stream.IntStream;
+
+public class CaesarCipher {
+
+    private final Logger log = LoggerFactory.getLogger(CaesarCipher.class);
+
+    private static final char LETTER_A = 'a';
+    private static final char LETTER_Z = 'z';
+    private static final int ALPHABET_SIZE = LETTER_Z - LETTER_A + 1;
+    private static final double[] ENGLISH_LETTERS_PROBABILITIES = {0.073, 0.009, 0.030, 0.044, 0.130, 0.028, 0.016, 0.035, 0.074, 0.002, 0.003, 0.035, 0.025, 0.078, 0.074, 0.027, 0.003, 0.077, 0.063, 0.093, 0.027, 0.013, 0.016, 0.005, 0.019, 0.001};
+
+    public String cipher(String message, int offset) {
+        StringBuilder result = new StringBuilder();
+
+        for (char character : message.toCharArray()) {
+            if (character != ' ') {
+                int originalAlphabetPosition = character - LETTER_A;
+                int newAlphabetPosition = (originalAlphabetPosition + offset) % ALPHABET_SIZE;
+                char newCharacter = (char) (LETTER_A + newAlphabetPosition);
+                result.append(newCharacter);
+            } else {
+                result.append(character);
+            }
+        }
+
+        return result.toString();
+    }
+
+    public String decipher(String message, int offset) {
+        return cipher(message, ALPHABET_SIZE - (offset % ALPHABET_SIZE));
+    }
+
+    public int breakCipher(String message) {
+        return probableOffset(chiSquares(message));
+    }
+
+    private double[] chiSquares(String message) {
+        double[] expectedLettersFrequencies = expectedLettersFrequencies(message.length());
+
+        double[] chiSquares = new double[ALPHABET_SIZE];
+
+        for (int offset = 0; offset < chiSquares.length; offset++) {
+            String decipheredMessage = decipher(message, offset);
+            long[] lettersFrequencies = observedLettersFrequencies(decipheredMessage);
+            double chiSquare = new ChiSquareTest().chiSquare(expectedLettersFrequencies, lettersFrequencies);
+            chiSquares[offset] = chiSquare;
+        }
+
+        return chiSquares;
+    }
+
+    private long[] observedLettersFrequencies(String message) {
+        return IntStream.rangeClosed(LETTER_A, LETTER_Z)
+          .mapToLong(letter -> countLetter((char) letter, message))
+          .toArray();
+    }
+
+    private long countLetter(char letter, String message) {
+        return message.chars()
+          .filter(character -> character == letter)
+          .count();
+    }
+
+    private double[] expectedLettersFrequencies(int messageLength) {
+        return Arrays.stream(ENGLISH_LETTERS_PROBABILITIES)
+          .map(probability -> probability * messageLength)
+          .toArray();
+    }
+
+    private int probableOffset(double[] chiSquares) {
+        int probableOffset = 0;
+        for (int offset = 0; offset < chiSquares.length; offset++) {
+            log.debug(String.format("Chi-Square for offset %d: %.2f", offset, chiSquares[offset]));
+            if (chiSquares[offset] < chiSquares[probableOffset]) {
+                probableOffset = offset;
+            }
+        }
+
+        return probableOffset;
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/gradientdescent/GradientDescent.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/gradientdescent/GradientDescent.java
@@ -0,0 +1,33 @@
+package com.baeldung.algorithms.gradientdescent;
+
+import java.util.function.Function;
+
+public class GradientDescent {
+
+    private final double precision = 0.000001;
+
+    public double findLocalMinimum(Function<Double, Double> f, double initialX) {
+        double stepCoefficient = 0.1;
+        double previousStep = 1.0;
+        double currentX = initialX;
+        double previousX = initialX;
+        double previousY = f.apply(previousX);
+        int iter = 100;
+
+        currentX += stepCoefficient * previousY;
+
+        while (previousStep > precision && iter > 0) {
+            iter--;
+            double currentY = f.apply(currentX);
+            if (currentY > previousY) {
+                stepCoefficient = -stepCoefficient / 2;
+            }
+            previousX = currentX;
+            currentX += stepCoefficient * previousY;
+            previousY = currentY;
+            previousStep = StrictMath.abs(currentX - previousX);
+        }
+        return currentX;
+    }
+
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/greedy/Follower.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/greedy/Follower.java
@@ -0,0 +1,20 @@
+package com.baeldung.algorithms.greedy;
+
+import lombok.Getter;
+
+public class Follower {
+
+    @Getter String username;
+    @Getter long count;
+    
+    public Follower(String username, long count) {
+        super();
+        this.username = username;
+        this.count = count;
+    }
+    
+    @Override
+    public String toString() {
+        return "User: " + username + ", Followers: " + count + "\n\r" ; 
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/greedy/FollowersPath.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/greedy/FollowersPath.java
@@ -0,0 +1,44 @@
+package com.baeldung.algorithms.greedy;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class FollowersPath {
+
+    private List<Follower> accounts;
+    private long count;
+    
+    public FollowersPath() {
+        super();
+        this.accounts = new ArrayList<>();
+    }
+    
+    public List<Follower> getAccounts() {
+        return accounts;
+    }
+    public long getCount() {
+        return count;
+    }
+    
+    public void addFollower(String username, long count) {
+        accounts.add(new Follower(username, count));
+    }
+    
+    public void addCount(long count) {
+        this.count += count;
+    }
+    
+    @Override
+    public String toString() {
+        String details = "";
+        for(Follower a : accounts) {
+            details+=a.toString() + ", ";
+        }
+        
+        return "Total: " + count + ", \n\r" +
+                " Details: { " + "\n\r" + 
+                details + "\n\r" + 
+                " }";
+    }
+    
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/greedy/GreedyAlgorithm.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/greedy/GreedyAlgorithm.java
@@ -0,0 +1,43 @@
+package com.baeldung.algorithms.greedy;
+
+import java.util.List;
+
+public class GreedyAlgorithm {
+
+    int currentLevel = 0;
+    final int maxLevel = 3; 
+    SocialConnector sc;
+    FollowersPath fp;
+    
+    public GreedyAlgorithm(SocialConnector sc) {
+        super();
+        this.sc = sc;
+        this.fp = new FollowersPath();
+    }
+    
+    public long findMostFollowersPath(String account) {
+        long max = 0;
+        SocialUser toFollow = null;
+        
+        List<SocialUser> followers = sc.getFollowers(account);
+        for (SocialUser el : followers) {
+            long followersCount = el.getFollowersCount();
+            if (followersCount > max) {
+                toFollow = el;
+                max = followersCount;
+            }
+        }
+        
+        if (currentLevel < maxLevel - 1) {
+            currentLevel++;
+            max += findMostFollowersPath(toFollow.getUsername());
+            return max;
+        } else {
+            return max;
+        }            
+    }
+    
+    public FollowersPath getFollowers() {
+        return fp;
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/greedy/NonGreedyAlgorithm.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/greedy/NonGreedyAlgorithm.java
@@ -0,0 +1,43 @@
+package com.baeldung.algorithms.greedy;
+
+import java.util.List;
+
+public class NonGreedyAlgorithm {
+
+    int currentLevel = 0;
+    final int maxLevel = 3; 
+    SocialConnector tc;
+    
+    public NonGreedyAlgorithm(SocialConnector tc, int level) {
+        super();
+        this.tc = tc;
+        this.currentLevel = level;
+    }
+      
+    public long findMostFollowersPath(String account) {
+        List<SocialUser> followers = tc.getFollowers(account);
+        long total = currentLevel > 0 ? followers.size() : 0;
+
+        if (currentLevel < maxLevel ) {
+            currentLevel++;
+
+            long[] count = new long[followers.size()];
+            int i = 0;
+            for (SocialUser el : followers) {
+                NonGreedyAlgorithm sub = new NonGreedyAlgorithm(tc, currentLevel);
+                count[i] = sub.findMostFollowersPath(el.getUsername());
+                i++;
+            }
+            
+            long max = 0;
+            for (; i > 0; i--) {
+                if (count[i-1] > max )
+                    max = count[i-1];
+            }
+            
+            return total + max;
+        }
+        
+        return total;
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/greedy/SocialConnector.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/greedy/SocialConnector.java
@@ -0,0 +1,36 @@
+package com.baeldung.algorithms.greedy;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import lombok.Getter;
+import lombok.Setter;
+
+public class SocialConnector {
+    private boolean isCounterEnabled = true;
+    private int counter = 4;
+    @Getter @Setter List<SocialUser> users;
+    
+    public SocialConnector() {
+        users = new ArrayList<>();
+    }
+    
+    public boolean switchCounter() {
+        this.isCounterEnabled = !this.isCounterEnabled;
+        return this.isCounterEnabled;
+    }
+    
+    public List<SocialUser> getFollowers(String account) {
+        if (counter < 0)
+            throw new IllegalStateException ("API limit reached");
+        else {
+            if(this.isCounterEnabled) counter--;
+            for(SocialUser user : users) {
+                if (user.getUsername().equals(account)) {
+                    return user.getFollowers();
+                }
+            }
+        }
+        return new ArrayList<>();
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/greedy/SocialUser.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/greedy/SocialUser.java
@@ -0,0 +1,38 @@
+package com.baeldung.algorithms.greedy;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import lombok.Getter;
+
+public class SocialUser {
+
+    @Getter private String username;
+    @Getter private List<SocialUser> followers;
+
+    public SocialUser(String username) {
+        super();
+        this.username = username;
+        this.followers = new ArrayList<>();
+    }
+    
+    public SocialUser(String username, List<SocialUser> followers) {
+        super();
+        this.username = username;
+        this.followers = followers;
+    }
+    
+    public long getFollowersCount() {
+        return followers.size();
+    }
+    
+    public void addFollowers(List<SocialUser> followers) {
+        this.followers.addAll(followers);
+    }
+    
+    @Override
+    public boolean equals(Object obj) {
+        return ((SocialUser) obj).getUsername().equals(username);
+    }
+    
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/kruskal/CycleDetector.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/kruskal/CycleDetector.java
@@ -0,0 +1,72 @@
+package com.baeldung.algorithms.kruskal;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class CycleDetector {
+
+    List<DisjointSetInfo> nodes;
+
+    public CycleDetector(int totalNodes) {
+        initDisjointSets(totalNodes);
+    }
+
+    public boolean detectCycle(Integer u, Integer v) {
+        Integer rootU = pathCompressionFind(u);
+        Integer rootV = pathCompressionFind(v);
+        if (rootU.equals(rootV)) {
+            return true;
+        }
+        unionByRank(rootU, rootV);
+        return false;
+    }
+
+    private void initDisjointSets(int totalNodes) {
+        nodes = new ArrayList<>(totalNodes);
+        for (int i = 0; i < totalNodes; i++) {
+            nodes.add(new DisjointSetInfo(i));
+        }
+    }
+
+    private Integer find(Integer node) {
+        Integer parent = nodes.get(node).getParentNode();
+        if (parent.equals(node)) {
+            return node;
+        } else {
+            return find(parent);
+        }
+    }
+
+    private Integer pathCompressionFind(Integer node) {
+        DisjointSetInfo setInfo = nodes.get(node);
+        Integer parent = setInfo.getParentNode();
+        if (parent.equals(node)) {
+            return node;
+        } else {
+            Integer parentNode = find(parent);
+            setInfo.setParentNode(parentNode);
+            return parentNode;
+        }
+    }
+
+    private void union(Integer rootU, Integer rootV) {
+        DisjointSetInfo setInfoU = nodes.get(rootU);
+        setInfoU.setParentNode(rootV);
+    }
+
+    private void unionByRank(int rootU, int rootV) {
+        DisjointSetInfo setInfoU = nodes.get(rootU);
+        DisjointSetInfo setInfoV = nodes.get(rootV);
+        int rankU = setInfoU.getRank();
+        int rankV = setInfoV.getRank();
+        if (rankU < rankV) {
+            setInfoU.setParentNode(rootV);
+        } else {
+            setInfoV.setParentNode(rootU);
+            if (rankU == rankV) {
+                setInfoU.setRank(rankU + 1);
+            }
+        }
+    }
+
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/kruskal/DisjointSetInfo.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/kruskal/DisjointSetInfo.java
@@ -0,0 +1,28 @@
+package com.baeldung.algorithms.kruskal;
+
+public class DisjointSetInfo {
+
+    private Integer parentNode;
+    private int rank;
+
+    DisjointSetInfo(Integer nodeNumber) {
+        setParentNode(nodeNumber);
+        setRank(1);
+    }
+
+    public Integer getParentNode() {
+        return parentNode;
+    }
+
+    public void setParentNode(Integer parentNode) {
+        this.parentNode = parentNode;
+    }
+
+    public int getRank() {
+        return rank;
+    }
+
+    public void setRank(int rank) {
+        this.rank = rank;
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/kruskal/Kruskal.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/kruskal/Kruskal.java
@@ -0,0 +1,53 @@
+package com.baeldung.algorithms.kruskal;
+
+import com.google.common.graph.EndpointPair;
+import com.google.common.graph.MutableValueGraph;
+import com.google.common.graph.ValueGraph;
+import com.google.common.graph.ValueGraphBuilder;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Set;
+
+public class Kruskal {
+
+    public ValueGraph<Integer, Double> minSpanningTree(ValueGraph<Integer, Double> graph) {
+
+        return spanningTree(graph, true);
+    }
+
+    public ValueGraph<Integer, Double> maxSpanningTree(ValueGraph<Integer, Double> graph) {
+        return spanningTree(graph, false);
+    }
+
+    private ValueGraph<Integer, Double> spanningTree(ValueGraph<Integer, Double> graph, boolean minSpanningTree) {
+        Set<EndpointPair<Integer>> edges = graph.edges();
+        List<EndpointPair<Integer>> edgeList = new ArrayList<>(edges);
+
+        if (minSpanningTree) {
+            edgeList.sort(Comparator.comparing(e -> graph.edgeValue(e).get()));
+        } else {
+            edgeList.sort(Collections.reverseOrder(Comparator.comparing(e -> graph.edgeValue(e).get())));
+        }
+
+        int totalNodes = graph.nodes().size();
+        CycleDetector cycleDetector = new CycleDetector(totalNodes);
+        int edgeCount = 0;
+
+        MutableValueGraph<Integer, Double> spanningTree = ValueGraphBuilder.undirected().build();
+        for (EndpointPair<Integer> edge : edgeList) {
+            if (cycleDetector.detectCycle(edge.nodeU(), edge.nodeV())) {
+                continue;
+            }
+            spanningTree.putEdgeValue(edge.nodeU(), edge.nodeV(), graph.edgeValue(edge).get());
+            edgeCount++;
+            if (edgeCount == totalNodes - 1) {
+                break;
+            }
+        }
+        return spanningTree;
+    }
+
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/linkedlist/LinkedListReversal.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/linkedlist/LinkedListReversal.java
@@ -0,0 +1,30 @@
+package com.baeldung.algorithms.linkedlist;
+
+public class LinkedListReversal {
+
+    ListNode reverseList(ListNode head) {
+        ListNode previous = null;
+        ListNode current = head;
+        while (current != null) {
+            ListNode nextElement = current.getNext();
+            current.setNext(previous);
+            previous = current;
+            current = nextElement;
+        }
+        return previous;
+    }
+
+    ListNode reverseListRecursive(ListNode head) {
+        if (head == null) {
+            return null;
+        }
+        if (head.getNext() == null) {
+            return head;
+        }
+        ListNode node = reverseListRecursive(head.getNext());
+        head.getNext().setNext(head);
+        head.setNext(null);
+        return node;
+    }
+
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/linkedlist/ListNode.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/linkedlist/ListNode.java
@@ -0,0 +1,28 @@
+package com.baeldung.algorithms.linkedlist;
+
+public class ListNode {
+
+    private int data;
+    private ListNode next;
+
+    ListNode(int data) {
+        this.data = data;
+        this.next = null;
+    }
+
+    public int getData() {
+        return data;
+    }
+
+    public ListNode getNext() {
+        return next;
+    }
+
+    public void setData(int data) {
+        this.data = data;
+    }
+
+    public void setNext(ListNode next) {
+        this.next = next;
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/minheapmerge/HeapNode.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/minheapmerge/HeapNode.java
@@ -0,0 +1,13 @@
+package com.baeldung.algorithms.minheapmerge;
+
+public class HeapNode {
+
+    int element;
+    int arrayIndex;
+    int nextElementIndex = 1;
+
+    public HeapNode(int element, int arrayIndex) {
+        this.element = element;
+        this.arrayIndex = arrayIndex;
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/minheapmerge/MinHeap.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/minheapmerge/MinHeap.java
@@ -0,0 +1,88 @@
+package com.baeldung.algorithms.minheapmerge;
+
+public class MinHeap {
+
+    HeapNode[] heapNodes;
+
+    public MinHeap(HeapNode heapNodes[]) {
+        this.heapNodes = heapNodes;
+        heapifyFromLastLeafsParent();
+    }
+
+    void heapifyFromLastLeafsParent() {
+        int lastLeafsParentIndex = getParentNodeIndex(heapNodes.length);
+        while (lastLeafsParentIndex >= 0) {
+            heapify(lastLeafsParentIndex);
+            lastLeafsParentIndex--;
+        }
+    }
+
+    void heapify(int index) {
+        int leftNodeIndex = getLeftNodeIndex(index);
+        int rightNodeIndex = getRightNodeIndex(index);
+        int smallestElementIndex = index;
+        if (leftNodeIndex < heapNodes.length && heapNodes[leftNodeIndex].element < heapNodes[index].element) {
+            smallestElementIndex = leftNodeIndex;
+        }
+        if (rightNodeIndex < heapNodes.length && heapNodes[rightNodeIndex].element < heapNodes[smallestElementIndex].element) {
+            smallestElementIndex = rightNodeIndex;
+        }
+        if (smallestElementIndex != index) {
+            swap(index, smallestElementIndex);
+            heapify(smallestElementIndex);
+        }
+    }
+
+    int getParentNodeIndex(int index) {
+        return (index - 1) / 2;
+    }
+
+    int getLeftNodeIndex(int index) {
+        return (2 * index + 1);
+    }
+
+    int getRightNodeIndex(int index) {
+        return (2 * index + 2);
+    }
+
+    HeapNode getRootNode() {
+        return heapNodes[0];
+    }
+
+    void heapifyFromRoot() {
+        heapify(0);
+    }
+
+    void swap(int i, int j) {
+        HeapNode temp = heapNodes[i];
+        heapNodes[i] = heapNodes[j];
+        heapNodes[j] = temp;
+    }
+    
+    static int[] merge(int[][] array) {
+        HeapNode[] heapNodes = new HeapNode[array.length];
+        int resultingArraySize = 0;
+
+        for (int i = 0; i < array.length; i++) {
+            HeapNode node = new HeapNode(array[i][0], i);
+            heapNodes[i] = node;
+            resultingArraySize += array[i].length;
+        }
+        
+        MinHeap minHeap = new MinHeap(heapNodes);
+        int[] resultingArray = new int[resultingArraySize];
+
+        for (int i = 0; i < resultingArraySize; i++) {
+            HeapNode root = minHeap.getRootNode();
+            resultingArray[i] = root.element;
+
+            if (root.nextElementIndex < array[root.arrayIndex].length) {
+                root.element = array[root.arrayIndex][root.nextElementIndex++];
+            } else {
+                root.element = Integer.MAX_VALUE;
+            }
+            minHeap.heapifyFromRoot();
+        }
+        return resultingArray;
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/play2048/Board.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/play2048/Board.java
@@ -0,0 +1,208 @@
+package com.baeldung.algorithms.play2048;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class Board {
+    private static final Logger LOG = LoggerFactory.getLogger(Board.class);
+
+    private final int[][] board;
+
+    private final int score;
+
+    public Board(int size) {
+        assert(size > 0);
+
+        this.board = new int[size][];
+        this.score = 0;
+
+        for (int x = 0; x < size; ++x) {
+            this.board[x] = new int[size];
+            for (int y = 0; y < size; ++y) {
+                board[x][y] = 0;
+            }
+        }
+    }
+
+    private Board(int[][] board, int score) {
+        this.score = score;
+        this.board = new int[board.length][];
+
+        for (int x = 0; x < board.length; ++x) {
+            this.board[x] = Arrays.copyOf(board[x], board[x].length);
+        }
+    }
+
+    public int getSize() {
+        return board.length;
+    }
+
+    public int getScore() {
+        return score;
+    }
+
+    public int getCell(Cell cell) {
+        int x = cell.getX();
+        int y = cell.getY();
+        assert(x >= 0 && x < board.length);
+        assert(y >= 0 && y < board.length);
+
+        return board[x][y];
+    }
+
+    public boolean isEmpty(Cell cell) {
+        return getCell(cell) == 0;
+    }
+
+    public List<Cell> emptyCells() {
+        List<Cell> result = new ArrayList<>();
+        for (int x = 0; x < board.length; ++x) {
+            for (int y = 0; y < board[x].length; ++y) {
+                Cell cell = new Cell(x, y);
+                if (isEmpty(cell)) {
+                    result.add(cell);
+                }
+            }
+        }
+        return result;
+    }
+
+    public Board placeTile(Cell cell, int number) {
+        if (!isEmpty(cell)) {
+            throw new IllegalArgumentException("That cell is not empty");
+        }
+
+        Board result = new Board(this.board, this.score);
+        result.board[cell.getX()][cell.getY()] = number;
+        return result;
+    }
+
+    public Board move(Move move) {
+        // Clone the board
+        int[][] tiles = new int[this.board.length][];
+        for (int x = 0; x < this.board.length; ++x) {
+            tiles[x] = Arrays.copyOf(this.board[x], this.board[x].length);
+        }
+
+        LOG.debug("Before move: {}", Arrays.deepToString(tiles));
+        // If we're doing an Left/Right move then transpose the board to make it a Up/Down move
+        if (move == Move.LEFT || move == Move.RIGHT) {
+            tiles = transpose(tiles);
+            LOG.debug("After transpose: {}", Arrays.deepToString(tiles));
+        }
+        // If we're doing a Right/Down move then reverse the board.
+        // With the above we're now always doing an Up move
+        if (move == Move.DOWN || move == Move.RIGHT) {
+            tiles = reverse(tiles);
+            LOG.debug("After reverse: {}", Arrays.deepToString(tiles));
+        }
+        LOG.debug("Ready to move: {}", Arrays.deepToString(tiles));
+
+        // Shift everything up
+        int[][] result = new int[tiles.length][];
+        int newScore = 0;
+        for (int x = 0; x < tiles.length; ++x) {
+            LinkedList<Integer> thisRow = new LinkedList<>();
+            for (int y = 0; y < tiles[0].length; ++y) {
+                if (tiles[x][y] > 0) {
+                    thisRow.add(tiles[x][y]);
+                }
+            }
+
+            LOG.debug("Unmerged row: {}", thisRow);
+            LinkedList<Integer> newRow = new LinkedList<>();
+            while (thisRow.size() >= 2) {
+                int first = thisRow.pop();
+                int second = thisRow.peek();
+                LOG.debug("Looking at numbers {} and {}", first, second);
+                if (second == first) {
+                    LOG.debug("Numbers match, combining");
+                    int newNumber = first * 2;
+                    newRow.add(newNumber);
+                    newScore += newNumber;
+                    thisRow.pop();
+                } else {
+                    LOG.debug("Numbers don't match");
+                    newRow.add(first);
+                }
+            }
+            newRow.addAll(thisRow);
+            LOG.debug("Merged row: {}", newRow);
+
+            result[x] = new int[tiles[0].length];
+            for (int y = 0; y < tiles[0].length; ++y) {
+                if (newRow.isEmpty()) {
+                    result[x][y] = 0;
+                } else {
+                    result[x][y] = newRow.pop();
+                }
+            }
+        }
+        LOG.debug("After moves: {}", Arrays.deepToString(result));
+
+        // Un-reverse the board
+        if (move == Move.DOWN || move == Move.RIGHT) {
+            result = reverse(result);
+            LOG.debug("After reverse: {}", Arrays.deepToString(result));
+        }
+        // Un-transpose the board
+        if (move == Move.LEFT || move == Move.RIGHT) {
+            result = transpose(result);
+            LOG.debug("After transpose: {}", Arrays.deepToString(result));
+        }
+        return new Board(result, this.score + newScore);
+    }
+
+    private static int[][] transpose(int[][] input) {
+        int[][] result = new int[input.length][];
+
+        for (int x = 0; x < input.length; ++x) {
+            result[x] = new int[input[0].length];
+            for (int y = 0; y < input[0].length; ++y) {
+                result[x][y] = input[y][x];
+            }
+        }
+
+        return result;
+    }
+
+    private static int[][] reverse(int[][] input) {
+        int[][] result = new int[input.length][];
+
+        for (int x = 0; x < input.length; ++x) {
+            result[x] = new int[input[0].length];
+            for (int y = 0; y < input[0].length; ++y) {
+                result[x][y] = input[x][input.length - y - 1];
+            }
+        }
+
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return Arrays.deepToString(board);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        Board board1 = (Board) o;
+        return Arrays.deepEquals(board, board1.board);
+    }
+
+    @Override
+    public int hashCode() {
+        return Arrays.deepHashCode(board);
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/play2048/Cell.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/play2048/Cell.java
@@ -0,0 +1,26 @@
+package com.baeldung.algorithms.play2048;
+
+import java.util.StringJoiner;
+
+public class Cell {
+    private int x;
+    private int y;
+
+    public Cell(int x, int y) {
+        this.x = x;
+        this.y = y;
+    }
+
+    public int getX() {
+        return x;
+    }
+
+    public int getY() {
+        return y;
+    }
+
+    @Override
+    public String toString() {
+        return new StringJoiner(", ", Cell.class.getSimpleName() + "[", "]").add("x=" + x).add("y=" + y).toString();
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/play2048/Computer.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/play2048/Computer.java
@@ -0,0 +1,27 @@
+package com.baeldung.algorithms.play2048;
+
+import java.security.SecureRandom;
+import java.util.List;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class Computer {
+    private static final Logger LOG = LoggerFactory.getLogger(Computer.class);
+
+    private final SecureRandom rng = new SecureRandom();
+
+    public Board makeMove(Board input) {
+        List<Cell> emptyCells = input.emptyCells();
+        LOG.info("Number of empty cells: {}", emptyCells.size());
+
+        double numberToPlace = rng.nextDouble();
+        LOG.info("New number probability: {}", numberToPlace);
+
+        int indexToPlace = rng.nextInt(emptyCells.size());
+        Cell cellToPlace = emptyCells.get(indexToPlace);
+        LOG.info("Placing number into empty cell: {}", cellToPlace);
+
+        return input.placeTile(cellToPlace, numberToPlace >= 0.9 ? 4 : 2);
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/play2048/Human.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/play2048/Human.java
@@ -0,0 +1,126 @@
+package com.baeldung.algorithms.play2048;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import org.apache.commons.math3.util.Pair;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class Human {
+    private static final Logger LOG = LoggerFactory.getLogger(Human.class);
+
+    public Board makeMove(Board input) {
+        // For each move in MOVE
+        //   Generate board from move
+        //   Generate Score for Board
+        // Return board with the best score
+        //
+        // Generate Score
+        //   If Depth Limit
+        //     Return Final Score
+        //   Total Score = 0
+        //   For every empty square in new board
+        //     Generate board with "2" in square
+        //       Calculate Score
+        //       Total Score += (Score * 0.9)
+        //     Generate board with "4" in square
+        //       Calculate Score
+        //       Total Score += (Score * 0.1)
+        //
+        // Calculate Score
+        //   For each move in MOVE
+        //     Generate board from move
+        //     Generate score for board
+        //   Return the best generated score
+
+        return Arrays.stream(Move.values())
+            .parallel()
+            .map(input::move)
+            .filter(board -> !board.equals(input))
+            .max(Comparator.comparingInt(board -> generateScore(board, 0)))
+            .orElse(input);
+    }
+
+    private int generateScore(Board board, int depth) {
+        if (depth >= 3) {
+            int finalScore = calculateFinalScore(board);
+            LOG.debug("Final score for board {}: {}", board,finalScore);
+            return finalScore;
+        }
+
+        return board.emptyCells().stream()
+            .parallel()
+            .flatMap(cell -> Stream.of(new Pair<>(cell, 2), new Pair<>(cell, 4)))
+            .mapToInt(move -> {
+                LOG.debug("Simulating move {} at depth {}", move, depth);
+                Board newBoard = board.placeTile(move.getFirst(), move.getSecond());
+                int boardScore = calculateScore(newBoard, depth + 1);
+                int calculatedScore = (int) (boardScore * (move.getSecond() == 2 ? 0.9 : 0.1));
+                LOG.debug("Calculated score for board {} and move {} at depth {}: {}", newBoard, move, depth, calculatedScore);
+                return calculatedScore;
+            })
+            .sum();
+    }
+
+    private int calculateScore(Board board, int depth) {
+        return Arrays.stream(Move.values())
+            .parallel()
+            .map(board::move)
+            .filter(moved -> !moved.equals(board))
+            .mapToInt(newBoard -> generateScore(newBoard, depth))
+            .max()
+            .orElse(0);
+    }
+
+    private int calculateFinalScore(Board board) {
+        List<List<Integer>> rowsToScore = new ArrayList<>();
+        for (int i = 0; i < board.getSize(); ++i) {
+            List<Integer> row = new ArrayList<>();
+            List<Integer> col = new ArrayList<>();
+
+            for (int j = 0; j < board.getSize(); ++j) {
+                row.add(board.getCell(new Cell(i, j)));
+                col.add(board.getCell(new Cell(j, i)));
+            }
+
+            rowsToScore.add(row);
+            rowsToScore.add(col);
+        }
+
+        return rowsToScore.stream()
+            .parallel()
+            .mapToInt(row -> {
+                List<Integer> preMerged = row.stream()
+                    .filter(value -> value != 0)
+                    .collect(Collectors.toList());
+
+                int numMerges = 0;
+                int monotonicityLeft = 0;
+                int monotonicityRight = 0;
+                for (int i = 0; i < preMerged.size() - 1; ++i) {
+                    Integer first = preMerged.get(i);
+                    Integer second = preMerged.get(i + 1);
+                    if (first.equals(second)) {
+                        ++numMerges;
+                    } else if (first > second) {
+                        monotonicityLeft += first - second;
+                    } else {
+                        monotonicityRight += second - first;
+                    }
+                }
+
+                int score = 1000;
+                score += 250 * row.stream().filter(value -> value == 0).count();
+                score += 750 * numMerges;
+                score -= 10 * row.stream().mapToInt(value -> value).sum();
+                score -= 50 * Math.min(monotonicityLeft, monotonicityRight);
+                return score;
+            })
+            .sum();
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/play2048/Move.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/play2048/Move.java
@@ -0,0 +1,8 @@
+package com.baeldung.algorithms.play2048;
+
+public enum Move {
+    UP,
+    DOWN,
+    LEFT,
+    RIGHT
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/play2048/Play2048.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/play2048/Play2048.java
@@ -0,0 +1,73 @@
+package com.baeldung.algorithms.play2048;
+
+public class Play2048 {
+    private static final int SIZE = 4;
+    private static final int INITIAL_NUMBERS = 2;
+
+    public static void main(String[] args) {
+        // The board and players
+        Board board = new Board(SIZE);
+        Computer computer = new Computer();
+        Human human = new Human();
+
+        // The computer has two moves first
+        System.out.println("Setup");
+        System.out.println("=====");
+        for (int i = 0; i < INITIAL_NUMBERS; ++i) {
+            board = computer.makeMove(board);
+        }
+
+        printBoard(board);
+        do {
+            board = human.makeMove(board);
+            System.out.println("Human move");
+            System.out.println("==========");
+            printBoard(board);
+
+            board = computer.makeMove(board);
+            System.out.println("Computer move");
+            System.out.println("=============");
+            printBoard(board);
+        } while (!board.emptyCells().isEmpty());
+
+        System.out.println("Final Score: " + board.getScore());
+
+    }
+
+    private static void printBoard(Board board) {
+        StringBuilder topLines = new StringBuilder();
+        StringBuilder midLines = new StringBuilder();
+        for (int x = 0; x < board.getSize(); ++x) {
+            topLines.append("+--------");
+            midLines.append("|        ");
+        }
+        topLines.append("+");
+        midLines.append("|");
+
+
+        for (int y = 0; y < board.getSize(); ++y) {
+            System.out.println(topLines);
+            System.out.println(midLines);
+            for (int x = 0; x < board.getSize(); ++x) {
+                Cell cell = new Cell(x, y);
+                System.out.print("|");
+                if (board.isEmpty(cell)) {
+                    System.out.print("        ");
+                } else {
+                    StringBuilder output = new StringBuilder(Integer.toString(board.getCell(cell)));
+                    while (output.length() < 8) {
+                        output.append(" ");
+                        if (output.length() < 8) {
+                            output.insert(0, " ");
+                        }
+                    }
+                    System.out.print(output);
+                }
+            }
+            System.out.println("|");
+            System.out.println(midLines);
+        }
+        System.out.println(topLines);
+        System.out.println("Score: " + board.getScore());
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/topkelements/BruteForceTopKElementsFinder.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/topkelements/BruteForceTopKElementsFinder.java
@@ -0,0 +1,26 @@
+package com.baeldung.algorithms.topkelements;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class BruteForceTopKElementsFinder implements TopKElementsFinder<Integer> {
+
+    public List<Integer> findTopK(List<Integer> input, int k) {
+        List<Integer> array = new ArrayList<>(input);
+        List<Integer> topKList = new ArrayList<>();
+
+        for (int i = 0; i < k; i++) {
+            int maxIndex = 0;
+
+            for (int j = 1; j < array.size(); j++) {
+                if (array.get(j) > array.get(maxIndex)) {
+                    maxIndex = j;
+                }
+            }
+
+            topKList.add(array.remove(maxIndex));
+        }
+
+        return topKList;
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/topkelements/MaxHeapTopKElementsFinder.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/topkelements/MaxHeapTopKElementsFinder.java
@@ -0,0 +1,26 @@
+package com.baeldung.algorithms.topkelements;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.PriorityQueue;
+
+public class MaxHeapTopKElementsFinder implements TopKElementsFinder<Integer> {
+
+    public List<Integer> findTopK(List<Integer> input, int k) {
+        PriorityQueue<Integer> maxHeap = new PriorityQueue<>();
+
+        input.forEach(number -> {
+            maxHeap.add(number);
+
+            if (maxHeap.size() > k) {
+                maxHeap.poll();
+            }
+        });
+
+        List<Integer> topKList = new ArrayList<>(maxHeap);
+        Collections.reverse(topKList);
+
+        return topKList;
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/topkelements/TopKElementsFinder.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/topkelements/TopKElementsFinder.java
@@ -0,0 +1,7 @@
+package com.baeldung.algorithms.topkelements;
+
+import java.util.List;
+
+public interface TopKElementsFinder<T extends Comparable<T>> {
+    List<T> findTopK(List<T> input, int k);
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/topkelements/TreeSetTopKElementsFinder.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/topkelements/TreeSetTopKElementsFinder.java
@@ -0,0 +1,17 @@
+package com.baeldung.algorithms.topkelements;
+
+import java.util.Comparator;
+import java.util.List;
+import java.util.Set;
+import java.util.TreeSet;
+import java.util.stream.Collectors;
+
+public class TreeSetTopKElementsFinder implements TopKElementsFinder<Integer> {
+
+    public List<Integer> findTopK(List<Integer> input, int k) {
+        Set<Integer> sortedSet = new TreeSet<>(Comparator.reverseOrder());
+        sortedSet.addAll(input);
+
+        return sortedSet.stream().limit(k).collect(Collectors.toList());
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/main/resources/logback.xml
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/main/resources/logback.xml
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>
--- a/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/balancedbrackets/BalancedBracketsUsingDequeUnitTest.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/balancedbrackets/BalancedBracketsUsingDequeUnitTest.java
@@ -0,0 +1,82 @@
+package com.baeldung.algorithms.balancedbrackets;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class BalancedBracketsUsingDequeUnitTest {
+    private BalancedBracketsUsingDeque balancedBracketsUsingDeque;
+
+    @Before
+    public void setup() {
+        balancedBracketsUsingDeque = new BalancedBracketsUsingDeque();
+    }
+
+    @Test
+    public void givenNullInput_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingDeque.isBalanced(null);
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEmptyString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenInvalidCharacterString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("abc[](){}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenOddLengthString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("{{[]()}}}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEvenLengthString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("{{[]()}}}}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEvenLengthUnbalancedString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("{[(])}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenAnotherEvenLengthUnbalancedString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("{{}(");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEvenLengthBalancedString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("{[()]}");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenBalancedString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("{{[[(())]]}}");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenAnotherBalancedString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("{{([])}}");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenUnBalancedString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("{{)[](}}");
+        assertThat(result).isFalse();
+    }
+
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/balancedbrackets/BalancedBracketsUsingStringUnitTest.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/balancedbrackets/BalancedBracketsUsingStringUnitTest.java
@@ -0,0 +1,82 @@
+package com.baeldung.algorithms.balancedbrackets;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class BalancedBracketsUsingStringUnitTest {
+    private BalancedBracketsUsingString balancedBracketsUsingString;
+
+    @Before
+    public void setup() {
+        balancedBracketsUsingString = new BalancedBracketsUsingString();
+    }
+
+    @Test
+    public void givenNullInput_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingString.isBalanced(null);
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEmptyString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingString.isBalanced("");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenInvalidCharacterString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingString.isBalanced("abc[](){}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenOddLengthString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingString.isBalanced("{{[]()}}}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEvenLengthString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingString.isBalanced("{{[]()}}}}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEvenLengthUnbalancedString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingString.isBalanced("{[(])}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenAnotherEvenLengthUnbalancedString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingString.isBalanced("{{}(");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEvenLengthBalancedString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingString.isBalanced("{[()]}");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenBalancedString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingString.isBalanced("{{[[(())]]}}");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenAnotherBalancedString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingString.isBalanced("{{([])}}");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenUnBalancedString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingString.isBalanced("{{)[](}}");
+        assertThat(result).isFalse();
+    }
+
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/boruvka/BoruvkaUnitTest.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/boruvka/BoruvkaUnitTest.java
@@ -0,0 +1,37 @@
+package com.baeldung.algorithms.boruvka;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import com.google.common.graph.MutableValueGraph;
+import com.google.common.graph.ValueGraphBuilder;
+
+public class BoruvkaUnitTest {
+
+    private MutableValueGraph<Integer, Integer> graph;
+
+    @Before
+    public void setup() {
+        graph = ValueGraphBuilder.undirected()
+            .build();
+        graph.putEdgeValue(0, 1, 8);
+        graph.putEdgeValue(0, 2, 5);
+        graph.putEdgeValue(1, 2, 9);
+        graph.putEdgeValue(1, 3, 11);
+        graph.putEdgeValue(2, 3, 15);
+        graph.putEdgeValue(2, 4, 10);
+        graph.putEdgeValue(3, 4, 7);
+    }
+
+    @Test
+    public void givenInputGraph_whenBoruvkaPerformed_thenMinimumSpanningTree() {
+        BoruvkaMST boruvkaMST = new BoruvkaMST(graph);
+        MutableValueGraph<Integer, Integer> mst = boruvkaMST.getMST();
+
+        assertEquals(30, boruvkaMST.getTotalWeight());
+        assertEquals(4, mst.edges().size());
+    }
+
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/caesarcipher/CaesarCipherUnitTest.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/caesarcipher/CaesarCipherUnitTest.java
@@ -0,0 +1,83 @@
+package com.baeldung.algorithms.caesarcipher;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class CaesarCipherUnitTest {
+    private static final String SENTENCE = "he told me i could never teach a llama to drive";
+    private static final String SENTENCE_SHIFTED_THREE = "kh wrog ph l frxog qhyhu whdfk d oodpd wr gulyh";
+    private static final String SENTENCE_SHIFTED_TEN = "ro dyvn wo s myevn xofob dokmr k vvkwk dy nbsfo";
+
+    private CaesarCipher algorithm = new CaesarCipher();
+
+    @Test
+    void givenSentenceAndShiftThree_whenCipher_thenCipheredMessageWithoutOverflow() {
+        String cipheredSentence = algorithm.cipher(SENTENCE, 3);
+
+        assertThat(cipheredSentence)
+          .isEqualTo(SENTENCE_SHIFTED_THREE);
+    }
+
+    @Test
+    void givenSentenceAndShiftTen_whenCipher_thenCipheredMessageWithOverflow() {
+        String cipheredSentence = algorithm.cipher(SENTENCE, 10);
+
+        assertThat(cipheredSentence)
+          .isEqualTo(SENTENCE_SHIFTED_TEN);
+    }
+
+    @Test
+    void givenSentenceAndShiftThirtySix_whenCipher_thenCipheredLikeTenMessageWithOverflow() {
+        String cipheredSentence = algorithm.cipher(SENTENCE, 36);
+
+        assertThat(cipheredSentence)
+          .isEqualTo(SENTENCE_SHIFTED_TEN);
+    }
+
+    @Test
+    void givenSentenceShiftedThreeAndShiftThree_whenDecipher_thenOriginalSentenceWithoutOverflow() {
+        String decipheredSentence = algorithm.decipher(SENTENCE_SHIFTED_THREE, 3);
+
+        assertThat(decipheredSentence)
+          .isEqualTo(SENTENCE);
+    }
+
+    @Test
+    void givenSentenceShiftedTenAndShiftTen_whenDecipher_thenOriginalSentenceWithOverflow() {
+        String decipheredSentence = algorithm.decipher(SENTENCE_SHIFTED_TEN, 10);
+
+        assertThat(decipheredSentence)
+          .isEqualTo(SENTENCE);
+    }
+
+    @Test
+    void givenSentenceShiftedTenAndShiftThirtySix_whenDecipher_thenOriginalSentenceWithOverflow() {
+        String decipheredSentence = algorithm.decipher(SENTENCE_SHIFTED_TEN, 36);
+
+        assertThat(decipheredSentence)
+          .isEqualTo(SENTENCE);
+    }
+
+    @Test
+    void givenSentenceShiftedThree_whenBreakCipher_thenOriginalSentence() {
+        int offset = algorithm.breakCipher(SENTENCE_SHIFTED_THREE);
+
+        assertThat(offset)
+          .isEqualTo(3);
+
+        assertThat(algorithm.decipher(SENTENCE_SHIFTED_THREE, offset))
+          .isEqualTo(SENTENCE);
+    }
+
+    @Test
+    void givenSentenceShiftedTen_whenBreakCipher_thenOriginalSentence() {
+        int offset = algorithm.breakCipher(SENTENCE_SHIFTED_TEN);
+
+        assertThat(offset)
+          .isEqualTo(10);
+
+        assertThat(algorithm.decipher(SENTENCE_SHIFTED_TEN, offset))
+          .isEqualTo(SENTENCE);
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/gradientdescent/GradientDescentUnitTest.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/gradientdescent/GradientDescentUnitTest.java
@@ -0,0 +1,20 @@
+package com.baeldung.algorithms.gradientdescent;
+
+import static org.junit.Assert.assertTrue;
+
+import java.util.function.Function;
+
+import org.junit.Test;
+
+public class GradientDescentUnitTest {
+
+    @Test
+    public void givenFunction_whenStartingPointIsOne_thenLocalMinimumIsFound() {
+        Function<Double, Double> df = x ->
+            StrictMath.abs(StrictMath.pow(x, 3)) - (3 * StrictMath.pow(x, 2)) + x;
+        GradientDescent gd = new GradientDescent();
+        double res = gd.findLocalMinimum(df, 1);
+        assertTrue(res > 1.78);
+        assertTrue(res < 1.84);
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/greedy/GreedyAlgorithmUnitTest.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/greedy/GreedyAlgorithmUnitTest.java
@@ -0,0 +1,58 @@
+package com.baeldung.algorithms.greedy;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.Arrays;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class GreedyAlgorithmUnitTest {
+
+    private SocialConnector prepareNetwork() {
+        SocialConnector sc = new SocialConnector();
+        SocialUser root = new SocialUser("root");
+        SocialUser child1 = new SocialUser("child1");
+        SocialUser child2 = new SocialUser("child2");
+        SocialUser child3 = new SocialUser("child3");
+        SocialUser child21 = new SocialUser("child21");
+        SocialUser child211 = new SocialUser("child211");
+        SocialUser child2111 = new SocialUser("child2111");
+        SocialUser child31 = new SocialUser("child31");
+        SocialUser child311 = new SocialUser("child311");
+        SocialUser child3111 = new SocialUser("child3111");
+        child211.addFollowers(Arrays.asList(new SocialUser[]{child2111}));
+        child311.addFollowers(Arrays.asList(new SocialUser[]{child3111}));
+        child21.addFollowers(Arrays.asList(new SocialUser[]{child211}));
+        child31.addFollowers(Arrays.asList(new SocialUser[]{child311, 
+          new SocialUser("child312"), new SocialUser("child313"), new SocialUser("child314")}));
+        child1.addFollowers(Arrays.asList(new SocialUser[]{new SocialUser("child11"), new SocialUser("child12")}));
+        child2.addFollowers(Arrays.asList(new SocialUser[]{child21, new SocialUser("child22"), new SocialUser("child23")}));
+        child3.addFollowers(Arrays.asList(new SocialUser[]{child31}));
+        root.addFollowers(Arrays.asList(new SocialUser[]{child1, child2, child3}));
+        sc.setUsers(Arrays.asList(new SocialUser[]{root, child1, child2, child3, child21, child31, child311, child211}));
+        return sc;
+    }
+
+    @Test
+    public void greedyAlgorithmTest() {
+        GreedyAlgorithm ga = new GreedyAlgorithm(prepareNetwork());
+        assertEquals(ga.findMostFollowersPath("root"), 5);
+    }
+
+    @Test
+    public void nongreedyAlgorithmTest() {
+        NonGreedyAlgorithm nga = new NonGreedyAlgorithm(prepareNetwork(), 0);
+        Assertions.assertThrows(IllegalStateException.class, () -> {
+            nga.findMostFollowersPath("root");
+          });
+    }
+
+    @Test
+    public void nongreedyAlgorithmUnboundedTest() {
+        SocialConnector sc = prepareNetwork();
+        sc.switchCounter();
+        NonGreedyAlgorithm nga = new NonGreedyAlgorithm(sc, 0);
+        assertEquals(nga.findMostFollowersPath("root"), 6);
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/kruskal/KruskalUnitTest.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/kruskal/KruskalUnitTest.java
@@ -0,0 +1,67 @@
+package com.baeldung.algorithms.kruskal;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Before;
+import org.junit.Test;
+import com.google.common.graph.MutableValueGraph;
+import com.google.common.graph.ValueGraph;
+import com.google.common.graph.ValueGraphBuilder;
+import com.baeldung.algorithms.kruskal.Kruskal;
+
+public class KruskalUnitTest {
+
+    private MutableValueGraph<Integer, Double> graph;
+
+    @Before
+    public void setup() {
+        graph = ValueGraphBuilder.undirected().build();
+        graph.putEdgeValue(0, 1, 8.0);
+        graph.putEdgeValue(0, 2, 5.0);
+        graph.putEdgeValue(1, 2, 9.0);
+        graph.putEdgeValue(1, 3, 11.0);
+        graph.putEdgeValue(2, 3, 15.0);
+        graph.putEdgeValue(2, 4, 10.0);
+        graph.putEdgeValue(3, 4, 7.0);
+    }
+
+    @Test
+    public void givenGraph_whenMinimumSpanningTree_thenOutputCorrectResult() {
+        final Kruskal kruskal = new Kruskal();
+        ValueGraph<Integer, Double> spanningTree = kruskal.minSpanningTree(graph);
+
+        assertTrue(spanningTree.hasEdgeConnecting(0, 1));
+        assertTrue(spanningTree.hasEdgeConnecting(0, 2));
+        assertTrue(spanningTree.hasEdgeConnecting(2, 4));
+        assertTrue(spanningTree.hasEdgeConnecting(3, 4));
+        assertEquals(graph.edgeValue(0, 1), spanningTree.edgeValue(0, 1));
+        assertEquals(graph.edgeValue(0, 2), spanningTree.edgeValue(0, 2));
+        assertEquals(graph.edgeValue(2, 4), spanningTree.edgeValue(2, 4));
+        assertEquals(graph.edgeValue(3, 4), spanningTree.edgeValue(3, 4));
+
+        assertFalse(spanningTree.hasEdgeConnecting(1, 2));
+        assertFalse(spanningTree.hasEdgeConnecting(1, 3));
+        assertFalse(spanningTree.hasEdgeConnecting(2, 3));
+    }
+
+    @Test
+    public void givenGraph_whenMaximumSpanningTree_thenOutputCorrectResult() {
+        final Kruskal kruskal = new Kruskal();
+        ValueGraph<Integer, Double> spanningTree = kruskal.maxSpanningTree(graph);
+
+        assertTrue(spanningTree.hasEdgeConnecting(0, 1));
+        assertTrue(spanningTree.hasEdgeConnecting(1, 3));
+        assertTrue(spanningTree.hasEdgeConnecting(2, 3));
+        assertTrue(spanningTree.hasEdgeConnecting(2, 4));
+        assertEquals(graph.edgeValue(0, 1), spanningTree.edgeValue(0, 1));
+        assertEquals(graph.edgeValue(1, 3), spanningTree.edgeValue(1, 3));
+        assertEquals(graph.edgeValue(2, 3), spanningTree.edgeValue(2, 3));
+        assertEquals(graph.edgeValue(2, 4), spanningTree.edgeValue(2, 4));
+
+        assertFalse(spanningTree.hasEdgeConnecting(0, 2));
+        assertFalse(spanningTree.hasEdgeConnecting(1, 2));
+        assertFalse(spanningTree.hasEdgeConnecting(3, 4));
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/linkedlist/LinkedListReversalUnitTest.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/linkedlist/LinkedListReversalUnitTest.java
@@ -0,0 +1,59 @@
+package com.baeldung.algorithms.linkedlist;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+public class LinkedListReversalUnitTest {
+    @Test
+    public void givenLinkedList_whenIterativeReverse_thenOutputCorrectResult() {
+        ListNode head = constructLinkedList();
+        ListNode node = head;
+        for (int i = 1; i <= 5; i++) {
+            assertNotNull(node);
+            assertEquals(i, node.getData());
+            node = node.getNext();
+        }
+        LinkedListReversal reversal = new LinkedListReversal();
+        node = reversal.reverseList(head);
+        for (int i = 5; i >= 1; i--) {
+            assertNotNull(node);
+            assertEquals(i, node.getData());
+            node = node.getNext();
+        }
+    }
+
+    @Test
+    public void givenLinkedList_whenRecursiveReverse_thenOutputCorrectResult() {
+        ListNode head = constructLinkedList();
+        ListNode node = head;
+        for (int i = 1; i <= 5; i++) {
+            assertNotNull(node);
+            assertEquals(i, node.getData());
+            node = node.getNext();
+        }
+        LinkedListReversal reversal = new LinkedListReversal();
+        node = reversal.reverseListRecursive(head);
+        for (int i = 5; i >= 1; i--) {
+            assertNotNull(node);
+            assertEquals(i, node.getData());
+            node = node.getNext();
+        }
+    }
+
+    private ListNode constructLinkedList() {
+        ListNode head = null;
+        ListNode tail = null;
+        for (int i = 1; i <= 5; i++) {
+            ListNode node = new ListNode(i);
+            if (head == null) {
+                head = node;
+            } else {
+                tail.setNext(node);
+            }
+            tail = node;
+        }
+        return head;
+    }
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/minheapmerge/MinHeapUnitTest.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/minheapmerge/MinHeapUnitTest.java
@@ -0,0 +1,22 @@
+package com.baeldung.algorithms.minheapmerge;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
+
+import org.junit.Test;
+
+public class MinHeapUnitTest {
+
+    private final int[][] inputArray = { { 0, 6 }, { 1, 5, 10, 100 }, { 2, 4, 200, 650 } };
+    private final int[] expectedArray = { 0, 1, 2, 4, 5, 6, 10, 100, 200, 650 };
+
+    @Test
+    public void givenSortedArrays_whenMerged_thenShouldReturnASingleSortedarray() {
+        int[] resultArray = MinHeap.merge(inputArray);
+        
+        assertThat(resultArray.length, is(equalTo(10)));
+        assertThat(resultArray, is(equalTo(expectedArray)));
+    }
+    
+}
--- a/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/topkelements/TopKElementsFinderUnitTest.java
+++ b/algorithms-modules/algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/topkelements/TopKElementsFinderUnitTest.java
@@ -0,0 +1,46 @@
+package com.baeldung.algorithms.topkelements;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.assertj.core.api.Java6Assertions.assertThat;
+
+public class TopKElementsFinderUnitTest {
+    private final TopKElementsFinder<Integer> bruteForceFinder = new BruteForceTopKElementsFinder();
+    private final TopKElementsFinder<Integer> maxHeapFinder = new MaxHeapTopKElementsFinder();
+    private final TopKElementsFinder<Integer> treeSetFinder = new TreeSetTopKElementsFinder();
+
+    private final int k = 4;
+    private final List<Integer> distinctIntegers = Arrays.asList(1, 2, 3, 9, 7, 6, 12);
+    private final List<Integer> distinctIntegersTopK = Arrays.asList(9, 7, 6, 12);
+    private final List<Integer> nonDistinctIntegers = Arrays.asList(1, 2, 3, 3, 9, 9, 7, 6, 12);
+    private final List<Integer> nonDistinctIntegersTopK = Arrays.asList(9, 9, 7, 12);
+
+
+    @Test
+    public void givenArrayDistinctIntegers_whenBruteForceFindTopK_thenReturnKLargest() {
+        assertThat(bruteForceFinder.findTopK(distinctIntegers, k)).containsOnlyElementsOf(distinctIntegersTopK);
+    }
+
+    @Test
+    public void givenArrayDistinctIntegers_whenMaxHeapFindTopK_thenReturnKLargest() {
+        assertThat(maxHeapFinder.findTopK(distinctIntegers, k)).containsOnlyElementsOf(distinctIntegersTopK);
+    }
+
+    @Test
+    public void givenArrayDistinctIntegers_whenTreeSetFindTopK_thenReturnKLargest() {
+        assertThat(treeSetFinder.findTopK(distinctIntegers, k)).containsOnlyElementsOf(distinctIntegersTopK);
+    }
+
+    @Test
+    public void givenArrayNonDistinctIntegers_whenBruteForceFindTopK_thenReturnKLargest() {
+        assertThat(bruteForceFinder.findTopK(nonDistinctIntegers, k)).containsOnlyElementsOf(nonDistinctIntegersTopK);
+    }
+
+    @Test
+    public void givenArrayNonDistinctIntegers_whenMaxHeapFindTopK_thenReturnKLargest() {
+        assertThat(maxHeapFinder.findTopK(nonDistinctIntegers, k)).containsOnlyElementsOf(nonDistinctIntegersTopK);
+    }
+}