leetcode 129. 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.

将上面的值往下面传递

/** * 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 sumNumbers(TreeNode* root)     {        ret = 0;           if (root)            count(0, root);        return ret;       }private:    int ret;    void count(int last, TreeNode* root)    {        if (!root->left && !root->right)             ret += last * 10 + root->val;               if (root->left)            count(last * 10 + root->val, root->left);        if (root->right)            count(last * 10 + root->val, root->right);        }};