110. 平衡二叉树

题目链接：

https://leetcode-cn.com/problems/balanced-binary-tree/

解题思路：

/**
 * 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(maxDepth(root.left)-maxDepth(root.right))>1)
            return false;
        else
        {
            if(isBalanced(root.right)&&isBalanced(root.left))
                return true;
            else
                return false;
        }
    }
    public int maxDepth(TreeNode root)//计算树层高
    {
        if(root==null)
            return 0;
        return Math.max(maxDepth(root.left),maxDepth(root.right))+1;
    }
}