[leetcode 129] 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.

/** * 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) {        vector<int> res;        if (root == NULL) {            return 0;        }        dfs(root, res, 0);        return accumulate(res.begin(), res.end(), 0);    }    void dfs(TreeNode *root, vector<int> &res, int sum) {        if (root == NULL) {            return ;        }        if (!root->left && !root->right) {            sum = sum*10 + root->val;            res.push_back(sum);        }                sum  = sum*10 + root->val;        dfs(root->left, res, sum);        dfs(root->right, res, sum);        sum = sum/10;    }};