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Add data structures as a separate module (#3518)

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* Remove data structures from core-java

* Add data-structures

* Update README with links to articles

* Add parent module reference
This commit is contained in:
Fatos Morina
2018-03-17 09:41:50 +01:00
committed by Grzegorz Piwowarek
parent 2b50c4c341
commit 4c0a39a342
8 changed files with 29 additions and 0 deletions
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161
data-structures/src/main/java/com/baeldung/tree/BinaryTree.java Normal file
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package com.baeldung.tree;
import java.util.LinkedList;
import java.util.Queue;
public class BinaryTree {
Node root;
public void add(int value) {
root = addRecursive(root, value);
}
private Node addRecursive(Node current, int value) {
if (current == null) {
return new Node(value);
}
if (value < current.value) {
current.left = addRecursive(current.left, value);
} else if (value > current.value) {
current.right = addRecursive(current.right, value);
}
return current;
}
public boolean isEmpty() {
return root == null;
}
public int getSize() {
return getSizeRecursive(root);
}
private int getSizeRecursive(Node current) {
return current == null ? 0 : getSizeRecursive(current.left) + 1 + getSizeRecursive(current.right);
}
public boolean containsNode(int value) {
return containsNodeRecursive(root, value);
}
private boolean containsNodeRecursive(Node current, int value) {
if (current == null) {
return false;
}
if (value == current.value) {
return true;
}
return value < current.value
? containsNodeRecursive(current.left, value)
: containsNodeRecursive(current.right, value);
}
public void delete(int value) {
deleteRecursive(root, value);
}
private Node deleteRecursive(Node current, int value) {
if (current == null) {
return null;
}
if (value == current.value) {
// Case 1: no children
if (current.left == null && current.right == null) {
return null;
}
// Case 2: only 1 child
if (current.right == null) {
return current.left;
}
if (current.left == null) {
return current.right;
}
// Case 3: 2 children
int smallestValue = findSmallestValue(current.right);
current.value = smallestValue;
current.right = deleteRecursive(current.right, smallestValue);
return current;
}
if (value < current.value) {
current.left = deleteRecursive(current.left, value);
return current;
}
current.right = deleteRecursive(current.right, value);
return current;
}
private int findSmallestValue(Node root) {
return root.left == null ? root.value : findSmallestValue(root.left);
}
public void traverseInOrder(Node node) {
if (node != null) {
traverseInOrder(node.left);
System.out.print(" " + node.value);
traverseInOrder(node.right);
}
}
public void traversePreOrder(Node node) {
if (node != null) {
System.out.print(" " + node.value);
traversePreOrder(node.left);
traversePreOrder(node.right);
}
}
public void traversePostOrder(Node node) {
if (node != null) {
traversePostOrder(node.left);
traversePostOrder(node.right);
System.out.print(" " + node.value);
}
}
public void traverseLevelOrder() {
if (root == null) {
return;
}
Queue<Node> nodes = new LinkedList<>();
nodes.add(root);
while (!nodes.isEmpty()) {
Node node = nodes.remove();
System.out.print(" " + node.value);
if (node.left != null) {
nodes.add(node.left);
}
if (node.left != null) {
nodes.add(node.right);
}
}
}
class Node {
int value;
Node left;
Node right;
Node(int value) {
this.value = value;
right = null;
left = null;
}
}
}

62
data-structures/src/main/java/com/baeldung/trie/Trie.java Normal file
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package com.baeldung.trie;
public class Trie {
private TrieNode root;
Trie() {
root = new TrieNode();
}
public void insert(String word) {
TrieNode current = root;
for (int i = 0; i < word.length(); i++) {
current = current.getChildren().computeIfAbsent(word.charAt(i), c -> new TrieNode());
}
current.setEndOfWord(true);
}
public boolean delete(String word) {
return delete(root, word, 0);
}
public boolean containsNode(String word) {
TrieNode current = root;
for (int i = 0; i < word.length(); i++) {
char ch = word.charAt(i);
TrieNode node = current.getChildren().get(ch);
if (node == null) {
return false;
}
current = node;
}
return current.isEndOfWord();
}
public boolean isEmpty() {
return root == null;
}
private boolean delete(TrieNode current, String word, int index) {
if (index == word.length()) {
if (!current.isEndOfWord()) {
return false;
}
current.setEndOfWord(false);
return current.getChildren().isEmpty();
}
char ch = word.charAt(index);
TrieNode node = current.getChildren().get(ch);
if (node == null) {
return false;
}
boolean shouldDeleteCurrentNode = delete(node, word, index + 1);
if (shouldDeleteCurrentNode) {
current.getChildren().remove(ch);
return current.getChildren().isEmpty();
}
return false;
}
}

31
data-structures/src/main/java/com/baeldung/trie/TrieNode.java Normal file
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package com.baeldung.trie;
import java.util.HashMap;
import java.util.Map;
class TrieNode {
private Map<Character, TrieNode> children;
private boolean endOfWord;
public TrieNode() {
children = new HashMap<>();
endOfWord = false;
}
public Map<Character, TrieNode> getChildren() {
return children;
}
public void setChildren(Map<Character, TrieNode> children) {
this.children = children;
}
public boolean isEndOfWord() {
return endOfWord;
}
public void setEndOfWord(boolean endOfWord) {
this.endOfWord = endOfWord;
}
}

119
data-structures/src/test/java/com/baeldung/tree/BinaryTreeTest.java Normal file
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package com.baeldung.tree;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;
import org.junit.Test;
public class BinaryTreeTest {
@Test
public void givenABinaryTree_WhenAddingElements_ThenTreeNotEmpty() {
BinaryTree bt = createBinaryTree();
assertTrue(!bt.isEmpty());
}
@Test
public void givenABinaryTree_WhenAddingElements_ThenTreeContainsThoseElements() {
BinaryTree bt = createBinaryTree();
assertTrue(bt.containsNode(6));
assertTrue(bt.containsNode(4));
assertFalse(bt.containsNode(1));
}
@Test
public void givenABinaryTree_WhenAddingExistingElement_ThenElementIsNotAdded() {
BinaryTree bt = createBinaryTree();
int initialSize = bt.getSize();
assertTrue(bt.containsNode(3));
bt.add(3);
assertEquals(initialSize, bt.getSize());
}
@Test
public void givenABinaryTree_WhenLookingForNonExistingElement_ThenReturnsFalse() {
BinaryTree bt = createBinaryTree();
assertFalse(bt.containsNode(99));
}
@Test
public void givenABinaryTree_WhenDeletingElements_ThenTreeDoesNotContainThoseElements() {
BinaryTree bt = createBinaryTree();
assertTrue(bt.containsNode(9));
bt.delete(9);
assertFalse(bt.containsNode(9));
}
@Test
public void givenABinaryTree_WhenDeletingNonExistingElement_ThenTreeDoesNotDelete() {
BinaryTree bt = createBinaryTree();
int initialSize = bt.getSize();
assertFalse(bt.containsNode(99));
bt.delete(99);
assertFalse(bt.containsNode(99));
assertEquals(initialSize, bt.getSize());
}
@Test
public void givenABinaryTree_WhenTraversingInOrder_ThenPrintValues() {
BinaryTree bt = createBinaryTree();
bt.traverseInOrder(bt.root);
}
@Test
public void givenABinaryTree_WhenTraversingPreOrder_ThenPrintValues() {
BinaryTree bt = createBinaryTree();
bt.traversePreOrder(bt.root);
}
@Test
public void givenABinaryTree_WhenTraversingPostOrder_ThenPrintValues() {
BinaryTree bt = createBinaryTree();
bt.traversePostOrder(bt.root);
}
@Test
public void givenABinaryTree_WhenTraversingLevelOrder_ThenPrintValues() {
BinaryTree bt = createBinaryTree();
bt.traverseLevelOrder();
}
private BinaryTree createBinaryTree() {
BinaryTree bt = new BinaryTree();
bt.add(6);
bt.add(4);
bt.add(8);
bt.add(3);
bt.add(5);
bt.add(7);
bt.add(9);
return bt;
}
}

68
data-structures/src/test/java/com/baeldung/trie/TrieTest.java Normal file
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package com.baeldung.trie;
import org.junit.Test;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;
public class TrieTest {
@Test
public void whenEmptyTrie_thenNoElements() {
Trie trie = new Trie();
assertFalse(trie.isEmpty());
}
@Test
public void givenATrie_whenAddingElements_thenTrieNotEmpty() {
Trie trie = createExampleTrie();
assertFalse(trie.isEmpty());
}
@Test
public void givenATrie_whenAddingElements_thenTrieHasThoseElements() {
Trie trie = createExampleTrie();
assertFalse(trie.containsNode("3"));
assertFalse(trie.containsNode("vida"));
assertTrue(trie.containsNode("Programming"));
assertTrue(trie.containsNode("is"));
assertTrue(trie.containsNode("a"));
assertTrue(trie.containsNode("way"));
assertTrue(trie.containsNode("of"));
assertTrue(trie.containsNode("life"));
}
@Test
public void givenATrie_whenLookingForNonExistingElement_thenReturnsFalse() {
Trie trie = createExampleTrie();
assertFalse(trie.containsNode("99"));
}
@Test
public void givenATrie_whenDeletingElements_thenTreeDoesNotContainThoseElements() {
Trie trie = createExampleTrie();
assertTrue(trie.containsNode("Programming"));
trie.delete("Programming");
assertFalse(trie.containsNode("Programming"));
}
private Trie createExampleTrie() {
Trie trie = new Trie();
trie.insert("Programming");
trie.insert("is");
trie.insert("a");
trie.insert("way");
trie.insert("of");
trie.insert("life");
return trie;
}
}