LeetCode:Balanced Binary Tree

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.

分析：判断一颗二叉树是否是平衡的，dfs递归求解，递归的过程中顺便求得树的高度本文地址

 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     bool isBalanced(TreeNode *root) {
13         // IMPORTANT: Please reset any member data you declared, as
14         // the same Solution instance will be reused for each test case.
15         if(root == NULL)return true;
16         if(height(root) == -1)return false;
17         else return true;
18     }
19     //若root是平衡树，那么返回树的高度，否则返回-1
20     int height(TreeNode *root)
21     {
22         if(root->left == NULL && root->right == NULL)return 1;
23         int leftHeight = 0, rightHeight = 0;
24         if(root->left)
25             leftHeight = height(root->left);
26         if(leftHeight == -1)return -1;
27         if(root->right)
28             rightHeight = height(root->right);
29         if(rightHeight == -1)return -1;
30         if(abs(leftHeight-rightHeight) > 1)return -1;
31         return 1+max(leftHeight, rightHeight);
32     }
33 };