LeetCode Path Sum

 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 hasPathSum(TreeNode *root, int sum) {
13         // Start typing your C/C++ solution below
14         // DO NOT write int main() function
15         if(root==0)
16             return false;
17         if(root->left==0&&root->right==0)
18         {
19             if(root->val==sum)
20                 return true;
21             return false;
22         }
23         if(root->left&&hasPathSum(root->left,sum-root->val))
24              return true;
25         if(root->right&&hasPathSum(root->right,sum-root->val))
26              return true;
27         return false;
28         
29     }
30 };
31 // 12ms
32 // 52ms
一定注意边界，root是否为空