Sum Root to Leaf Numbers--LeetCode

题目：

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.

思路：如果知道从根节点到所有叶子节点的路径上的数字，然后将这条路径转换为整数，将所有的路径转换的整数相加，就是所求的结果

void helper_leaf(BinTree* root,vector<int>& path,int& sum){if(root == NULL)return ;path.push_back(root->value);if(root->left == NULL && root->right == NULL){int tmp=0;for(int i=0;i<path.size();i++)tmp = tmp*10 + path[i];sum += tmp;//cout<<"tmp is "<<tmp<<endl; //return ;}helper_leaf(root->left,path,sum);helper_leaf(root->right,path,sum);path.pop_back();}int RootToLeaf(BinTree* root){if(root == NULL)return 0;vector<int> path;int sum=0;helper_leaf(root,path,sum);return sum;}