BalancedBinaryTree.java

/*
Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1. 
*/


import java.io.*;
import java.util.*;
public class BalancedBinaryTree {
	public static class TreeNode {
		int val;
		TreeNode left;
		TreeNode right;
		TreeNode(int x) { val = x; }
	}
	public static boolean isBalanced(TreeNode root) {
        if(root == null) return true;
        int l = depth(root.left, 0);
        int r = depth(root.right, 0);
        if(Math.abs(l-r) > 1) return false;
        return isBalanced(root.left) && isBalanced(root.right);
        
    }
    
    public static int depth(TreeNode root, int d){
        if(root == null){
            return d;
        }
        int l = depth(root.left, d+1);
        int r = depth(root.right, d+1);
        return l>r? l: r;
    }
	
	
	public static void main(String[] args) { 
		TreeNode root = new TreeNode(1);
		TreeNode node2 = new TreeNode(2);
		TreeNode node3 = new TreeNode(3);
		TreeNode node4 = new TreeNode(4);
		TreeNode node5 = new TreeNode(5);
		TreeNode node6 = new TreeNode(6);
		TreeNode node7 = new TreeNode(7);
		TreeNode node8 = new TreeNode(8);
		TreeNode node9 = new TreeNode(9);
		TreeNode node10 = new TreeNode(10);
		TreeNode node11 = new TreeNode(11);
		root.left = node2;
		root.right = node3;
		node2.left = node4;
		node2.right = node5;
		node3.left = node6;
		node3.right = node7;
		node4.left = node8;
		node4.right = node9;
		node5.left = node10;
		node5.right = node11;
		node6.left =  null;
		node6.right = null;
		node7.left = null;
		node7.right = null;
		node8.left = null;
		node8.right = null;
		node9.left = null;
		node9.right = null;
		node10.left = null;
		node10.right = null;
		node11.left = null;
		node11.right = null;
		boolean res = isBalanced(root);
		System.out.println("Is blanced:" + res);
		return;
	}	
}