Java-FOP/level_order_traversl_line_by_line.java at master · Jasmine-21/Java-FOP · GitHub

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package github;
import java.util.LinkedList;
import java.util.Queue;

public class level_order_traversl_line_by_line {
	//level order traversal line by line
	/*using one queue*/
	  static class Node {
	    int data;
	    Node left;
	    Node right;

	    Node(int data) {
	      this.data = data;
	      left = null;
	      right = null;
	    }
	  }
	  static void levelOrder(Node root) {
	    if (root == null)
	      return;

	    Queue<Node> q = new LinkedList<>();
	    q.add(root);
	    q.add(null);
	    while (!q.isEmpty()) {
	   Node curr = q.poll();
	      if (curr == null) {
	        if (!q.isEmpty()) {
	          q.add(null);
	          System.out.print("$ ");
	        }
	      } else {
	        if (curr.left != null)
	          q.add(curr.left);

	        if (curr.right != null)
	          q.add(curr.right);

	        System.out.print(curr.data + " ");
	      }
	    }
        System.out.print("$ ");

	  }
	  /* using two queue
	   *
	   * static void levelOrder(Node root)
    {
        Queue<Node> q1 = new LinkedList<Node>();
        Queue<Node> q2 = new LinkedList<Node>();

        if (root == null)
            return;
          q1.add(root);
          while (!q1.isEmpty() || !q2.isEmpty())
        {
            while (!q1.isEmpty())
            {
                if (q1.peek().left != null)
                    q2.add(q1.peek().left);
                  if (q1.peek().right != null)
                    q2.add(q1.peek().right);

                System.out.print(q1.peek().data + " ");
                q1.remove();
            }
            System.out.println();

            while (!q2.isEmpty())
            {

                if (q2.peek().left != null)
                    q1.add(q2.peek().left);


                if (q2.peek().right != null)
                    q1.add(q2.peek().right);

                System.out.print(q2.peek().data + " ");
                q2.remove();
            }
            System.out.println();
        }
        */

	  // Driver function
	  public static void main(String[] args) {

	    Node root = new Node(1);
	    root.left = new Node(2);
	    root.right = new Node(3);
	    root.left.left = new Node(4);
	    root.left.right = new Node(5);
	    root.right.right = new Node(6);

	    levelOrder(root);
	  }
	}