LeetCode之“树”：Balanced Binary Tree

　　题目链接

　　题目要求：

　　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.

　　这道题难度还好。具体程序（16ms）如下：

 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 isBalancedSub(root);
14     }
15
16     bool isBalancedSub(TreeNode *tree)
17     {
18         if(!tree)
19             return true;
20         if(abs(getHeight(tree->left) - getHeight(tree->right)) > 1)
21             return false;
22         return isBalancedSub(tree->left) && isBalancedSub(tree->right);
23     }
24
25     int getHeight(TreeNode *tree)
26     {
27         if(!tree)
28             return 0;
29
30         int m = getHeight(tree->left);
31         int n = getHeight(tree->right);
32         return (m > n) ? m + 1 : n + 1;
33     }
34 };