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 left and right subtrees of every node differ in height by no more than 1.

 

// Example 1:

// Given the following tree [3,9,20,null,null,15,7]:

//     3
//    / \
//   9  20
//     /  \
//    15   7
// Return true.

// Example 2:

// Given the following tree [1,2,2,3,3,null,null,4,4]:

//        1
//       / \
//      2   2
//     / \
//    3   3
//   / \
//  4   4
// Return false.


/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public boolean isBalanced(TreeNode root) {
        
         if(root == null){
             return true;
         }
        
        if(Math.abs(height(root.left) - height(root.right)) > 1){
            return false;
        }
         return isBalanced(root.left) && isBalanced(root.right);
    }
    
    
    public int height(TreeNode root){
    
    if(root == null){
            return 0;
        }
        
        int t1 = height(root.left);
        int t2 = height(root.right);
        
        return 1+Math.max(t1,t2);
    }
}