Balanced Binary Tree

题目来源LeetCode
题目描述

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.

这道题就是基础的判断平衡二叉树，就利用定义求左右深度再比较，代码如下：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
 int depth(TreeNode*root){
     if(root == NULL) return 0;
     int lp = depth(root->left);
     int rp = depth(root->right);
     if(lp > rp) return lp+1;
     else return rp+1;
 }

class Solution {
public:
    bool isBalanced(TreeNode* root) {
       if(root == NULL) return true;
       int lp = depth(root->left);
       int rp = depth(root->right);
       if(lp-rp > 1 || lp-rp < -1) return false;
       return isBalanced(root->left) && isBalanced(root->right);
    }
};