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Add a traversal algorithm #264

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126 changes: 126 additions & 0 deletions Traversals/BinaryTreeTraverse.java
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package Traversals;

import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;

/**
*
* @author Yolanda Tang (https://github.com/ReturnHttp402)
*
* This is pure Java implementation of tree traversal algorithms
*
*/
public class BinaryTreeTraverse {

public static class TreeNode{
public int nodeValue;
public TreeNode left;
public TreeNode right;

public TreeNode(int value){
this.nodeValue = value;
}
}
private static void insertRec(TreeNode latestRoot, TreeNode node) {

if (latestRoot.nodeValue > node.nodeValue) {
if (latestRoot.left == null) {
latestRoot.left = node;
return;
} else {
insertRec(latestRoot.left, node);
}
} else {
if (latestRoot.right == null) {
latestRoot.left = node;
return;
} else {
insertRec(latestRoot.right, node);
}
}
}
public static class BinarySearchTree {
public TreeNode root;

public void insert(int value) {
TreeNode node = new TreeNode(value);

if (root == null) {
root = node;
return;
}
insertRec(root,node);

}
}
public static void main(String[] args) {
System.out.println("\n********* Binary Tree Traversals ************\n");
Scanner in = new Scanner(System.in);
BinarySearchTree tree = new BinarySearchTree();
System.out.println("********Press N to stop entering at any point of time********");
while(true) {
if (in.next().equalsIgnoreCase("N")) {
break;
}
System.out.println("Enter the value of the node: ");
tree.insert(in.nextInt());
}

System.out.println("\n********* Depth First ************");
System.out.println("\n********* Pre Order Traversal ************");
preOrder(tree.root);

System.out.println("\n********* In Order Traversal ************");
inOrder(tree.root);

System.out.println("\n********* Post Order Traversal ************");
postOrder(tree.root);

System.out.println("\n********* Breadth First ************");
System.out.println("\n********* Level Order Traversal ************");
levelOrder(tree.root);
}
public static void preOrder(TreeNode node){
if(node == null) {
return;
}
System.out.print(node.nodeValue+",");
preOrder(node.left);
preOrder(node.right);
}
public static void inOrder(TreeNode node){
if(node == null){
return;
}
inOrder(node.left);
System.out.print(node.nodeValue+",");
inOrder(node.right);
}
public static void postOrder(TreeNode node){
if(node == null){
return;
}
postOrder(node.left);
postOrder(node.right);
System.out.print(node.nodeValue+",");
}
public static void levelOrder(TreeNode node){
Queue<TreeNode> queue = new LinkedList<>();
queue.offer(node);
while (!queue.isEmpty()){
TreeNode nodeDequeued = queue.peek();
System.out.print(nodeDequeued.nodeValue+",");
queue.poll();
if(nodeDequeued.left != null){
queue.offer(nodeDequeued.left);
}
if(nodeDequeued.right != null){
queue.offer(nodeDequeued.right);
}
}
}

}