Leetcode: isBalanced

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