[leetcode-129]Sum Root to Leaf Numbers（c++)

问题描述：
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.

分析：使用DFS，当递归到叶节点时，更新sum值。

代码如下：4ms

/** * 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 {    int sum = 0;public:    void solve(TreeNode* root,int cur){        if(!root)            return;        if(root->left==NULL&&root->right==NULL){//叶节点           cur = cur*10+root->val;           sum+=cur;            return;        }        solve(root->left,cur*10+root->val);        solve(root->right,cur*10+root->val);    }    int sumNumbers(TreeNode* root) {        if(!root)            return 0;        solve(root,0);        return sum;    }};