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.

求根到叶表示的所有数的和。

DFS

/** * 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:    void dfs(TreeNode* root,int &res,int now)    {        if(!root) return ;        if(!root->left && !root->right) res+=now*10+root->val;        dfs(root->left,res,now*10+root->val);        dfs(root->right,res,now*10+root->val);    }    int sumNumbers(TreeNode* root) {        int res=0;        dfs(root,res,0);        return res;    }};