leetcode—sum root to leaf number

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;

    }

};