[BAEL-9551] - Splitted algorithms into 4 modules

algorithms-sorting/.gitignore

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+/target/
+.settings/
+.classpath
+.project

algorithms-sorting/README.md

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+## Relevant articles:
+
+- [Bubble Sort in Java](http://www.baeldung.com/java-bubble-sort)
+- [Merge Sort in Java](https://www.baeldung.com/java-merge-sort)
+- [Quicksort Algorithm Implementation in Java](https://www.baeldung.com/java-quicksort)
+- [Insertion Sort in Java](https://www.baeldung.com/java-insertion-sort)
+

algorithms-sorting/pom.xml

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+<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>
+    <groupId>com.baeldung</groupId>
+    <artifactId>algorithms-sorting</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-math3</artifactId>
+            <version>${commons-math3.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>commons-codec</groupId>
+            <artifactId>commons-codec</artifactId>
+            <version>${commons-codec.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>${lombok.version}</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>io.jenetics</groupId>
+            <artifactId>jenetics</artifactId>
+            <version>${io.jenetics.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.jgrapht</groupId>
+            <artifactId>jgrapht-core</artifactId>
+            <version>${org.jgrapht.core.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>pl.allegro.finance</groupId>
+            <artifactId>tradukisto</artifactId>
+            <version>${tradukisto.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${org.assertj.core.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <pluginManagement>
+            <plugins>
+                <plugin>
+                    <groupId>org.codehaus.mojo</groupId>
+                    <artifactId>exec-maven-plugin</artifactId>
+                    <version>${exec-maven-plugin.version}</version>
+                </plugin>
+            </plugins>
+        </pluginManagement>
+    </build>
+
+    <reporting>
+        <plugins>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>cobertura-maven-plugin</artifactId>
+                <version>2.7</version>
+                <configuration>
+                    <instrumentation>
+                        <ignores>
+                            <ignore>com/baeldung/algorithms/dijkstra/*</ignore>
+                        </ignores>
+                        <excludes>
+                            <exclude>com/baeldung/algorithms/dijkstra/*</exclude>
+                        </excludes>
+                    </instrumentation>
+                </configuration>
+            </plugin>
+        </plugins>
+    </reporting>
+
+    <properties>
+        <lombok.version>1.16.12</lombok.version>
+        <commons-math3.version>3.6.1</commons-math3.version>
+        <tradukisto.version>1.0.1</tradukisto.version>
+        <io.jenetics.version>3.7.0</io.jenetics.version>
+        <org.jgrapht.core.version>1.0.1</org.jgrapht.core.version>
+        <org.assertj.core.version>3.9.0</org.assertj.core.version>
+        <commons-codec.version>1.11</commons-codec.version>
+    </properties>
+
+</project>

algorithms-sorting/roundUpToHundred/.gitignore

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+/bin/

algorithms-sorting/roundUpToHundred/src/com/java/src/RoundUpToHundred.java

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+package com.java.src;
+
+import java.util.Scanner;
+
+public class RoundUpToHundred {
+
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+        double input = scanner.nextDouble();
+        scanner.close();
+
+        RoundUpToHundred.round(input);
+    }
+
+    static long round(double input) {
+        long i = (long) Math.ceil(input);
+        return ((i + 99) / 100) * 100;
+    };
+
+}

algorithms-sorting/roundUpToHundred/src/com/java/src/RoundUpToHundredTest.java

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+package com.java.src;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class RoundUpToHundredTest {
+    @Test
+    public void givenInput_whenRound_thenRoundUpToTheNearestHundred() {
+        assertEquals("Rounded up to hundred", 100, RoundUpToHundred.round(99));
+        assertEquals("Rounded up to three hundred ", 300, RoundUpToHundred.round(200.2));
+        assertEquals("Returns same rounded value", 400, RoundUpToHundred.round(400));
+    }
+}

algorithms-sorting/src/main/java/com/baeldung/algorithms/bubblesort/BubbleSort.java

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+package com.baeldung.algorithms.bubblesort;
+
+import java.util.stream.IntStream;
+
+public class BubbleSort {
+
+    void bubbleSort(Integer[] arr) {
+        int n = arr.length;
+        IntStream.range(0, n - 1)
+          .flatMap(i -> IntStream.range(1, n - i))
+          .forEach(j -> {
+              if (arr[j - 1] > arr[j]) {
+                  int temp = arr[j];
+                  arr[j] = arr[j - 1];
+                  arr[j - 1] = temp;
+              }
+          });
+    }
+
+    void optimizedBubbleSort(Integer[] arr) {
+        int i = 0, n = arr.length;
+
+        boolean swapNeeded = true;
+        while (i < n - 1 && swapNeeded) {
+            swapNeeded = false;
+            for (int j = 1; j < n - i; j++) {
+                if (arr[j - 1] > arr[j]) {
+
+                    int temp = arr[j - 1];
+                    arr[j - 1] = arr[j];
+                    arr[j] = temp;
+                    swapNeeded = true;
+                }
+            }
+            if (!swapNeeded)
+                break;
+            i++;
+        }
+    }
+}

algorithms-sorting/src/main/java/com/baeldung/algorithms/heapsort/Heap.java

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+package com.baeldung.algorithms.heapsort;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class Heap<E extends Comparable<E>> {
+
+    private List<E> elements = new ArrayList<>();
+
+    public static <E extends Comparable<E>> List<E> sort(Iterable<E> elements) {
+        Heap<E> heap = of(elements);
+
+        List<E> result = new ArrayList<>();
+
+        while (!heap.isEmpty()) {
+            result.add(heap.pop());
+        }
+
+        return result;
+    }
+
+    public static <E extends Comparable<E>> Heap<E> of(E... elements) {
+        return of(Arrays.asList(elements));
+    }
+
+    public static <E extends Comparable<E>> Heap<E> of(Iterable<E> elements) {
+        Heap<E> result = new Heap<>();
+        for (E element : elements) {
+            result.add(element);
+        }
+        return result;
+    }
+
+    public void add(E e) {
+        elements.add(e);
+        int elementIndex = elements.size() - 1;
+        while (!isRoot(elementIndex) && !isCorrectChild(elementIndex)) {
+            int parentIndex = parentIndex(elementIndex);
+            swap(elementIndex, parentIndex);
+            elementIndex = parentIndex;
+        }
+    }
+
+    public E pop() {
+        if (isEmpty()) {
+            throw new IllegalStateException("You cannot pop from an empty heap");
+        }
+
+        E result = elementAt(0);
+
+        int lasElementIndex = elements.size() - 1;
+        swap(0, lasElementIndex);
+        elements.remove(lasElementIndex);
+
+        int elementIndex = 0;
+        while (!isLeaf(elementIndex) && !isCorrectParent(elementIndex)) {
+            int smallerChildIndex = smallerChildIndex(elementIndex);
+            swap(elementIndex, smallerChildIndex);
+            elementIndex = smallerChildIndex;
+        }
+
+        return result;
+    }
+
+    public boolean isEmpty() {
+        return elements.isEmpty();
+    }
+    
+    private boolean isRoot(int index) {
+        return index == 0;
+    }
+
+    private int smallerChildIndex(int index) {
+        int leftChildIndex = leftChildIndex(index);
+        int rightChildIndex = rightChildIndex(index);
+        
+        if (!isValidIndex(rightChildIndex)) {
+            return leftChildIndex;
+        }
+
+        if (elementAt(leftChildIndex).compareTo(elementAt(rightChildIndex)) < 0) {
+            return leftChildIndex;
+        }
+
+        return rightChildIndex;
+    }
+
+    private boolean isLeaf(int index) {
+        return !isValidIndex(leftChildIndex(index));
+    }
+
+    private boolean isCorrectParent(int index) {
+        return isCorrect(index, leftChildIndex(index)) && isCorrect(index, rightChildIndex(index));
+    }
+
+    private boolean isCorrectChild(int index) {
+        return isCorrect(parentIndex(index), index);
+    }
+
+    private boolean isCorrect(int parentIndex, int childIndex) {
+        if (!isValidIndex(parentIndex) || !isValidIndex(childIndex)) {
+            return true;
+        }
+
+        return elementAt(parentIndex).compareTo(elementAt(childIndex)) < 0;
+    }
+
+    private boolean isValidIndex(int index) {
+        return index < elements.size();
+    }
+
+    private void swap(int index1, int index2) {
+        E element1 = elementAt(index1);
+        E element2 = elementAt(index2);
+        elements.set(index1, element2);
+        elements.set(index2, element1);
+    }
+
+    private E elementAt(int index) {
+        return elements.get(index);
+    }
+
+    private int parentIndex(int index) {
+        return (index - 1) / 2;
+    }
+
+    private int leftChildIndex(int index) {
+        return 2 * index + 1;
+    }
+
+    private int rightChildIndex(int index) {
+        return 2 * index + 2;
+    }
+
+}

algorithms-sorting/src/main/java/com/baeldung/algorithms/insertionsort/InsertionSort.java

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+package com.baeldung.algorithms.insertionsort;
+
+public class InsertionSort {
+
+    public static void insertionSortImperative(int[] input) {
+        for (int i = 1; i < input.length; i++) {
+            int key = input[i];
+            int j = i - 1;
+            while (j >= 0 && input[j] > key) {
+                input[j + 1] = input[j];
+                j = j - 1;
+            }
+            input[j + 1] = key;
+        }
+    }
+
+    public static void insertionSortRecursive(int[] input) {
+        insertionSortRecursive(input, input.length);
+    }
+
+    private static void insertionSortRecursive(int[] input, int i) {
+        // base case
+        if (i <= 1) {
+            return;
+        }
+
+        // sort the first i - 1 elements of the array
+        insertionSortRecursive(input, i - 1);
+
+        // then find the correct position of the element at position i
+        int key = input[i - 1];
+        int j = i - 2;
+        // shifting the elements from their position by 1
+        while (j >= 0 && input[j] > key) {
+            input[j + 1] = input[j];
+            j = j - 1;
+        }
+        // inserting the key at the appropriate position
+        input[j + 1] = key;
+    }
+}

algorithms-sorting/src/main/java/com/baeldung/algorithms/mergesort/MergeSort.java

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+package com.baeldung.algorithms.mergesort;
+
+public class MergeSort {
+
+    public static void main(String[] args) {
+        int[] a = { 5, 1, 6, 2, 3, 4 };
+        mergeSort(a, a.length);
+        for (int i = 0; i < a.length; i++)
+            System.out.println(a[i]);
+    }
+
+    public static void mergeSort(int[] a, int n) {
+        if (n < 2)
+            return;
+        int mid = n / 2;
+        int[] l = new int[mid];
+        int[] r = new int[n - mid];
+
+        for (int i = 0; i < mid; i++) {
+            l[i] = a[i];
+        }
+        for (int i = mid; i < n; i++) {
+            r[i - mid] = a[i];
+        }
+        mergeSort(l, mid);
+        mergeSort(r, n - mid);
+
+        merge(a, l, r, mid, n - mid);
+    }
+
+    public static void merge(int[] a, int[] l, int[] r, int left, int right) {
+
+        int i = 0, j = 0, k = 0;
+
+        while (i < left && j < right) {
+
+            if (l[i] < r[j])
+                a[k++] = l[i++];
+            else
+                a[k++] = r[j++];
+
+        }
+
+        while (i < left)
+            a[k++] = l[i++];
+
+        while (j < right)
+            a[k++] = r[j++];
+    }
+}

algorithms-sorting/src/main/java/com/baeldung/algorithms/quicksort/QuickSort.java

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+package com.baeldung.algorithms.quicksort;
+
+public class QuickSort {
+
+    public static void quickSort(int arr[], int begin, int end)
+    {
+        if (begin < end) {
+            int partitionIndex = partition(arr, begin, end);
+
+            // Recursively sort elements of the 2 sub-arrays
+            quickSort(arr, begin, partitionIndex-1);
+            quickSort(arr, partitionIndex+1, end);
+        }
+    }
+
+    private static int partition(int arr[], int begin, int end)
+    {
+        int pivot = arr[end];
+        int i = (begin-1);
+
+        for (int j=begin; j<end; j++)
+        {
+            if (arr[j] <= pivot) {
+                i++;
+
+                int swapTemp = arr[i];
+                arr[i] = arr[j];
+                arr[j] = swapTemp;
+            }
+        }
+
+        int swapTemp = arr[i+1];
+        arr[i+1] = arr[end];
+        arr[end] = swapTemp;
+
+        return i+1;
+    }
+
+}

algorithms-sorting/src/main/java/com/baeldung/algorithms/quicksort/ThreeWayQuickSort.java

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+package com.baeldung.algorithms.quicksort;
+
+public class ThreeWayQuickSort {
+
+    public static void threeWayQuickSort(int[] a, int begin, int end)
+    {
+        if (end <= begin) return;
+
+        // partition
+        int i = begin;
+        int less = begin;
+        int greater = end;
+
+        while (i <= greater){
+            if (a[i] < a[less]) {
+                int tmp = a[i];
+                a[i] = a[less];
+                a[less] = tmp;
+
+                i++;
+                less++;
+            }
+            else if (a[less] < a[i])	{
+                int tmp = a[i];
+                a[i] = a[greater];
+                a[greater] = tmp;
+
+                greater--;
+            }
+            else {
+                i++;
+            }
+        }
+
+        threeWayQuickSort(a, begin, less - 1);
+        threeWayQuickSort(a, greater + 1, end);
+    }
+}

algorithms-sorting/src/main/resources/logback.xml

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+<?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>

algorithms-sorting/src/test/java/com/baeldung/algorithms/bubblesort/BubbleSortUnitTest.java

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+package com.baeldung.algorithms.bubblesort;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class BubbleSortUnitTest {
+
+    @Test
+    public void givenIntegerArray_whenSortedWithBubbleSort_thenGetSortedArray() {
+        Integer[] array = { 2, 1, 4, 6, 3, 5 };
+        Integer[] sortedArray = { 1, 2, 3, 4, 5, 6 };
+        BubbleSort bubbleSort = new BubbleSort();
+        bubbleSort.bubbleSort(array);
+        assertArrayEquals(array, sortedArray);
+    }
+
+    @Test
+    public void givenIntegerArray_whenSortedWithOptimizedBubbleSort_thenGetSortedArray() {
+        Integer[] array = { 2, 1, 4, 6, 3, 5 };
+        Integer[] sortedArray = { 1, 2, 3, 4, 5, 6 };
+        BubbleSort bubbleSort = new BubbleSort();
+        bubbleSort.optimizedBubbleSort(array);
+        assertArrayEquals(array, sortedArray);
+    }
+}

algorithms-sorting/src/test/java/com/baeldung/algorithms/heapsort/HeapUnitTest.java

@@ -0,0 +1,36 @@
+package com.baeldung.algorithms.heapsort;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.Test;
+
+public class HeapUnitTest {
+
+    @Test
+    public void givenNotEmptyHeap_whenPopCalled_thenItShouldReturnSmallestElement() {
+        // given
+        Heap<Integer> heap = Heap.of(3, 5, 1, 4, 2);
+
+        // when
+        int head = heap.pop();
+
+        // then
+        assertThat(head).isEqualTo(1);
+    }
+    
+    @Test
+    public void givenNotEmptyIterable_whenSortCalled_thenItShouldReturnElementsInSortedList() {
+        // given
+        List<Integer> elements = Arrays.asList(3, 5, 1, 4, 2);
+        
+        // when
+        List<Integer> sortedElements = Heap.sort(elements);
+        
+        // then
+        assertThat(sortedElements).isEqualTo(Arrays.asList(1, 2, 3, 4, 5));
+    }
+
+}

algorithms-sorting/src/test/java/com/baeldung/algorithms/insertionsort/InsertionSortUnitTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.algorithms.insertionsort;
+
+import com.baeldung.algorithms.insertionsort.InsertionSort;
+import org.junit.Test;
+
+import static org.junit.Assert.assertArrayEquals;
+
+public class InsertionSortUnitTest {
+
+    @Test
+    public void givenUnsortedArray_whenInsertionSortImperative_thenSortedAsc() {
+        int[] input = {6, 2, 3, 4, 5, 1};
+        InsertionSort.insertionSortImperative(input);
+        int[] expected = {1, 2, 3, 4, 5, 6};
+        assertArrayEquals("the two arrays are not equal", expected, input);
+    }
+
+    @Test
+    public void givenUnsortedArray_whenInsertionSortRecursive_thenSortedAsc() {
+        int[] input = {6, 4, 5, 2, 3, 1};
+        InsertionSort.insertionSortRecursive(input);
+        int[] expected = {1, 2, 3, 4, 5, 6};
+        assertArrayEquals("the two arrays are not equal", expected, input);
+    }
+}

algorithms-sorting/src/test/java/com/baeldung/algorithms/mergesort/MergeSortUnitTest.java

@@ -0,0 +1,17 @@
+package com.baeldung.algorithms.mergesort;
+
+import org.junit.Assert;
+
+import org.junit.Test;
+
+public class MergeSortUnitTest {
+
+    @Test
+    public void positiveTest() {
+        int[] actual = { 5, 1, 6, 2, 3, 4 };
+        int[] expected = { 1, 2, 3, 4, 5, 6 };
+        MergeSort.mergeSort(actual, actual.length);
+        Assert.assertArrayEquals(expected, actual);
+    }
+
+}

algorithms-sorting/src/test/java/com/baeldung/algorithms/quicksort/QuickSortUnitTest.java

@@ -0,0 +1,17 @@
+package com.baeldung.algorithms.quicksort;
+
+import com.baeldung.algorithms.quicksort.QuickSort;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class QuickSortUnitTest {
+
+    @Test
+    public void givenIntegerArray_whenSortedWithQuickSort_thenGetSortedArray() {
+        int[] actual = { 9, 5, 1, 0, 6, 2, 3, 4, 7, 8 };
+        int[] expected = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
+        QuickSort.quickSort(actual, 0, actual.length-1);
+        Assert.assertArrayEquals(expected, actual);
+    }
+
+}

algorithms-sorting/src/test/java/com/baeldung/algorithms/quicksort/ThreeWayQuickSortUnitTest.java

@@ -0,0 +1,15 @@
+package com.baeldung.algorithms.quicksort;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class ThreeWayQuickSortUnitTest {
+
+    @Test
+    public void givenIntegerArray_whenSortedWithThreeWayQuickSort_thenGetSortedArray() {
+        int[] actual = { 3, 5, 5, 5, 3, 7, 7, 3, 5, 5, 7, 3, 3 };
+        int[] expected = { 3, 3, 3, 3, 3, 5, 5, 5, 5, 5, 7, 7, 7 };
+        ThreeWayQuickSort.threeWayQuickSort(actual, 0, actual.length-1);
+        Assert.assertArrayEquals(expected, actual);
+    }
+}