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BinaryTree
//src: https://github.com/eugenp/tutorials/blob/5b5733239c06b595649324d744e97c6a2dc97d68/data-structures/src/main/java/com/baeldung/tree/BinaryTree.java
import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;
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) {
root = 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);
}
}
}
public void traverseInOrderWithoutRecursion() {
Stack<Node> stack = new Stack<Node>();
Node current = root;
stack.push(root);
while(! stack.isEmpty()) {
while(current.left != null) {
current = current.left;
stack.push(current);
}
current = stack.pop();
System.out.print(" " + current.value);
if(current.right != null) {
current = current.right;
stack.push(current);
}
}
}
public void traversePreOrderWithoutRecursion() {
Stack<Node> stack = new Stack<Node>();
Node current = root;
stack.push(root);
while(! stack.isEmpty()) {
current = stack.pop();
System.out.print(" " + current.value);
if(current.right != null)
stack.push(current.right);
if(current.left != null)
stack.push(current.left);
}
}
public void traversePostOrderWithoutRecursion() {
Stack<Node> stack = new Stack<Node>();
Node prev = root;
Node current = root;
stack.push(root);
while (!stack.isEmpty()) {
current = stack.peek();
boolean hasChild = (current.left != null || current.right != null);
boolean isPrevLastChild = (prev == current.right || (prev == current.left && current.right == null));
if (!hasChild || isPrevLastChild) {
current = stack.pop();
System.out.print(" " + current.value);
prev = current;
} else {
if (current.right != null) {
stack.push(current.right);
}
if (current.left != null) {
stack.push(current.left);
}
}
}
}
class Node {
int value;
Node left;
Node right;
Node(int value) {
this.value = value;
right = null;
left = null;
}
}
}
////////////
// src: https://github.com/eugenp/tutorials/blob/5b5733239c06b595649324d744e97c6a2dc97d68/data-structures/src/test/java/com/baeldung/tree/BinaryTreeUnitTest.java
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;
import org.junit.Test;
public class BinaryTreeUnitTest {
@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 it_deletes_the_root() {
int value = 12;
BinaryTree bt = new BinaryTree();
bt.add(value);
assertTrue(bt.containsNode(value));
bt.delete(value);
assertFalse(bt.containsNode(value));
}
@Test
public void givenABinaryTree_WhenTraversingInOrder_ThenPrintValues() {
BinaryTree bt = createBinaryTree();
bt.traverseInOrder(bt.root);
System.out.println();
bt.traverseInOrderWithoutRecursion();
}
@Test
public void givenABinaryTree_WhenTraversingPreOrder_ThenPrintValues() {
BinaryTree bt = createBinaryTree();
bt.traversePreOrder(bt.root);
System.out.println();
bt.traversePreOrderWithoutRecursion();
}
@Test
public void givenABinaryTree_WhenTraversingPostOrder_ThenPrintValues() {
BinaryTree bt = createBinaryTree();
bt.traversePostOrder(bt.root);
System.out.println();
bt.traversePostOrderWithoutRecursion();
}
@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;
}
}
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