[LeetCode] 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.

 

Solution:

/**

 * Definition for binary tree

 * struct TreeNode {

 *     int val;

 *     TreeNode *left;

 *     TreeNode *right;

 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}

 * };

 */

class Solution {

public:

    int sum = 0;

    int calc(int cur_value, TreeNode *node)

    {

        if(node == NULL)

            return 0;

        if(node -> left == NULL && node -> right == NULL)

        {

            sum += cur_value * 10 + node -> val;

        }

        else

        {

            if(node -> left != NULL)

                calc(cur_value * 10 + node -> val, node -> left);

            if(node -> right != NULL)

                calc(cur_value * 10 + node -> val, node -> right);

        }

    }

    

    int sumNumbers(TreeNode *root) {

        calc(0, root);

        return sum;

    }

};