Binary Tree Traversal - Level Order Using Queue

BinaryTreeLevelOrderTraversal.java

// prints the node value in binary tree at each level 
// prints all the node value in binary tree together
// prints tree in binary order
import java.util.Stack;
import java.util.Queue;
import java.util.LinkedList;

class Node {
    int data;
    Node left, right;

    public Node(int item) {
        data = item;
        left = null;
        right = null;
    }
}

class BinaryTree {

    Node root;

    void printLevelOrder() 
    {
       Queue<Node> queue = new LinkedList<Node>();
       queue.add(root);
       while(!queue.isEmpty()) {
           Node temp = queue.poll();
           System.out.print(temp.data + " ");
           if(temp.left != null) {
               queue.add(temp.left);
           }
           if(temp.right != null) {
               queue.add(temp.right);
           }
       } 
    }
    
    void printLevelOrderPerLevel() 
    {
       Queue<Node> queue = new LinkedList<Node>();
       queue.add(root);
       
        while(true){
           
           int size = queue.size();
           if(size == 0){
               break;
           }
           while( size > 0 ) {
               Node temp = queue.poll();
               System.out.print(temp.data + " ");
               if(temp.left != null) {
                   queue.add(temp.left);
               }
               if(temp.right != null) {
                   queue.add(temp.right);
               }
               size--;
           } 
           System.out.println();
       }
    }
    
    void spiralOrder() 
    {
       Stack<Node> s1 = new Stack<Node>();
       Stack<Node> s2 = new Stack<Node>();
       s1.push(root);
       
       
       while(!s1.isEmpty()|| !s2.isEmpty()) 
       {
          
          while(!s1.isEmpty()) 
          {
              Node temp = s1.pop();
              System.out.print(" " + temp.data + " ");
              
              if(temp.right != null) {
                  s2.push(temp.right);
              }
              if(temp.left != null) {
                  s2.push(temp.left);
              }
          }
           
          while(!s2.isEmpty()) 
          {
              Node temp = s2.pop();
              System.out.print(" " + temp.data + " ");
              
              if(temp.left != null) {
                  s1.push(temp.left);
              }
              if(temp.right != null) {
                  s1.push(temp.right);
              }
          }
       }
       
    }
    
    public static void main(String args[]) 
    {
        BinaryTree tree_level = new BinaryTree();
        tree_level.root = new Node(1);
        tree_level.root.left = new Node(2);
        tree_level.root.right = new Node(3);
        tree_level.root.left.left = new Node(4);
        tree_level.root.left.right = new Node(5);
        
        tree_level.root.right.left = new Node(6);
        tree_level.root.right.right = new Node(7);
        
        System.out.println("Level order traversal of binary tree is - ");
        tree_level.printLevelOrder();
        System.out.println();
        System.out.println("Level order traversal of binary tree per level is  - ");
        tree_level.printLevelOrderPerLevel();
        System.out.println(" Tree in Spiral Order ");
        tree_level.spiralOrder();
    }
}