题目如下：

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.

解题思路：

一个带有记录功能的DFS，随时记录当前数字，当前和，返回即可

代码如下：

/**

* Definition for binary tree

* struct TreeNode {

*     int val;

*     TreeNode *left;

*     TreeNode *right;

*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}

* };

*/

class Solution {

public:

int sumNumbers(TreeNode *root) {

// Start typing your C/C++ solution below

// DO NOT write int main() function

int sum = 0;

int curNumber = 0;

sumNumbers_my(root,curNumber,sum);

return sum;

}

void sumNumbers_my(TreeNode *root,int &curNumber,int &sum)

{

if(root == NULL)return;

curNumber = curNumber*10+root->val;

int curNumber_bk = curNumber;

if(root ->left== NULL&&root->right ==NULL)

{

sum+= curNumber;return;

}

sumNumbers_my(root->left,curNumber,sum);

curNumber = curNumber_bk;

sumNumbers_my(root->right,curNumber,sum);

return;

}

};