[129]Sum Root to Leaf Numbers

【题目描述】

Given a binary tree containing digits from 

0-9

 only, each root-to-leaf path
could represent a number.

An example is the root-to-leaf path 

1->2->3

 which represents the number 

123

.

Find the total sum of all root-to-leaf numbers.

For example,

1
/ \
2   3

The root-to-leaf path 

1->2

 represents the number 

12

.

The root-to-leaf path 

1->3

 represents the number 

13

.

Return the sum = 12 + 13 = 

25

.
【思路】
用递归实现深搜就可以了，一次AC。

【代码】

/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector<int> ans;
void dfs(TreeNode* root,int sum){
if(root->left==NULL&&root->right==NULL) ans.push_back(sum*10+root->val);
if(root->left!=NULL) dfs(root->left,sum*10+root->val);
if(root->right!=NULL) dfs(root->right,sum*10+root->val);
}
int sumNumbers(TreeNode* root) {
int ret=0;
if(root==NULL) return 0;
dfs(root,0);
for(int i=0;i<ans.size();i++){
ret+=ans[i];
}
return ret;
}
};