【leetcode】Balanced Binary Tree

Question ： 

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.

Anwser 1 ：       

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    int maxHeight(TreeNode *root) {          if (root == NULL) return 0;                    int left = maxHeight(root->left) + 1;          int right = maxHeight(root->right) + 1;          return left > right ? left : right;      }         bool isBalanced(TreeNode *root) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        if (root == NULL) return true;                while(root != NULL)        {            int left = maxHeight(root->left);            int right = maxHeight(root->right);            if (abs(left - right) >= 2) {                return false;            }                        return isBalanced(root->left) && isBalanced(root->right);        }    }};