【树】129. 求根到叶子节点数字之和

 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     int sumNumbers(TreeNode* root) 
13     {
14         return sumNumbersHelper(root, 0);
15     }
16 
17     int sumNumbersHelper(TreeNode *root, int num)
18     {
19         if (NULL == root)
20         {
21             return 0;
22         }
23 
24         num = num * 10 + root->val;
25 
26         if (root->left == NULL && root->right == NULL)
27         {
28             return num;
29         }
30         else
31         {
32             return sumNumbersHelper(root->left, num) + sumNumbersHelper(root->right, num);
33         }
34     }
35 };