Sum Root to Leaf Numbers

题目：

Sum Root to Leaf Numbers

 

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：DFS

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:   int sumNumbers(TreeNode* root) {int sum=0;int total=0;dfs_sum(root,sum,total);return total;}void dfs_sum(TreeNode* root,int &sum,int &total){if (root==NULL){return;}sum=sum*10+root->val;dfs_sum(root->left,sum,total);dfs_sum(root->right,sum,total);if (root->left==NULL&&root->right==NULL){total+=sum;}   sum=sum/10;}};