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.

给定一个二叉树仅包含数字0-9，每一个从根到叶子的路径代表一个数字。

例如从根到叶的路径为1->2->3，那么这个数为123.

得出所有根叶树的和。

写一个函数遍历每条路径，得出每条路径代表的数字，然后加入全局变量sum中，代码如下：

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {    int sum=0;public:    int sumNumbers(TreeNode *root) {        if(root==NULL) return 0;        getsum(root,0);        return sum;    }public:    void getsum(TreeNode *root,int cursum)    {        cursum=cursum*10+root->val;        if(root->left==NULL && root->right==NULL) sum+=cursum;        if(root->left) getsum(root->left,cursum);        if(root->right) getsum(root->right,cursum);    }};