[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.

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {private:    int sum;public:    int sumNumbers(TreeNode *root) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        sum = 0;                if(root == NULL)            return sum;                pathNum(root, 0);        return sum;    }        void pathNum(TreeNode *root, int currNum)    {        if(root == NULL)            return;                    currNum = currNum * 10 + root->val;                    if(root->left == NULL && root->right == NULL)        {            sum += currNum;        }        else        {            pathNum(root->left, currNum);            pathNum(root->right, currNum);        }    }};