[LeetCode]Balanced Binary Tree

 1 /**
 2  * Definition for a binary tree node.
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     bool isBalanced(TreeNode* root) {
13         return height(root) >= 0;
14     }
15     
16     int height(TreeNode *root) {
17         if (root == nullptr) return 0;
18         
19         int left = height(root->left);
20         int right = height(root->right);
21         
22         if (left < 0 || right < 0 || abs(left - right) > 1) {
23             return -1;
24         }
25         
26         return max(left, right) + 1;
27     }
28 };