LeetCode 110: Balanced Binary Tree

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.

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    
    public boolean isBalanced(TreeNode root) {
        if (root == null)
            return true;
        
        // The depth of current two subtrees should not differ by more than 1.
        if (Math.abs(maxDepth(root.left) - maxDepth(root.right)) > 1)
            return false;
        
        // The depth of the two subtrees of every node never differ by more than 1.    
        return isBalanced(root.left) && isBalanced(root.right);
    }
    
    private int maxDepth(TreeNode root)
    {
        if (root == null)
            return 0;
            
        return Math.max(maxDepth(root.left), maxDepth(root.right)) + 1;
    }
}