IsCompleteBinaryTree.java

package com.interview.tree;

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

/**
 * http://www.geeksforgeeks.org/check-if-a-given-binary-tree-is-complete-tree-or-not/
 * Test cases:
 * A node with only right child
 * A node with only left child
 * A node with both left and right child
 */
public class IsCompleteBinaryTree {

    public boolean isComplete(Node root){
        Queue<Node> queue = new LinkedList<Node>();
        queue.offer(root);
        boolean foundFirstNonFull = false;
        while(!queue.isEmpty()){
            root = queue.poll();
            if(foundFirstNonFull){
                if(root.left != null || root.right != null){
                    return false;
                }
                continue;
            }
            if(root.left != null && root.right != null){
                queue.offer(root.left);
                queue.offer(root.right);
            }else if(root.left != null){
                queue.offer(root.left);
                foundFirstNonFull = true;
            }else if(root.right != null){
                return false;
            }else{
                foundFirstNonFull = true;
            }
        }
        return true;
    }
    
    public static void main(String args[]){
        BinaryTree bt = new BinaryTree();
        Node head = null;
        head = bt.addNode(3, head);
        head = bt.addNode(-6, head);
        head = bt.addNode(7, head);
        head = bt.addNode(-10, head);
        head = bt.addNode(-15, head);
        head = bt.addNode(-4, head);
        head = bt.addNode(4, head);
        head = bt.addNode(11, head);
        head = bt.addNode(-9, head);
            
        IsCompleteBinaryTree icbt = new IsCompleteBinaryTree();
        System.out.println(icbt.isComplete(head));
    }
}