[Leetcode] Sum Root to Leaf Numbers

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.

要求计算每条路径得到的数字之和，发现跟遍历二叉树很类似，每当到达叶节点时记录当前路径上的值。

vector<int> res;void sumNumbers(TreeNode *x, int n){n=n*10+ x->val;                         //转换路径上经过的数字if(x->left)sumNumbers(x->left, n);         //递归遍历if(x->right)sumNumbers(x->right, n);if(x->left==NULL && x->right==NULL)      //只有到叶节点时才保存res.push_back(n);}int sumNumbers(TreeNode *root){    int sum=0;    if(root ==NULL) return sum;    sumNumbers(root,0);    for(int i=0; i<res.size(); i++)        sum+=res[i];    return sum;}