[Leetcode][Tree][Balanced Binary Tree]

 1 /**
 2  * Definition for binary tree
 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     int height(TreeNode * root) {
13         int hleft, hright;
14         hleft = hright = 0;
15         if (root->left != NULL) {
16             hleft = height(root->left);
17         }
18         if (root->right != NULL) {
19             hright = height(root->right);
20         }
21         if (hleft < 0 || hright < 0 || abs(hleft - hright) > 1) {
22             return -1;
23         }
24         return max(hleft, hright) + 1;
25     }
26     bool isBalanced(TreeNode *root) {
27         if (root == NULL) {
28             return true;
29         } else {
30             return height(root) >= 0;
31         }
32     }
33 };