leetcode Sum Root to Leaf Numbers

原题链接：https://leetcode.com/problems/sum-root-to-leaf-numbers/

Description

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 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 ans;
int sumNumbers(TreeNode* root) {
if (!root) return 0;
ans = 0;
dfs(root, 0);
return ans;
}
void dfs(TreeNode *x, int v) {
if (!x) return;
if (!x->left && !x->right) {
ans += x->val + v * 10;
}
dfs(x->left, v * 10 + x->val);
dfs(x->right, v * 10 + x->val);
}
};