LeetCode (Sum Root to Leaf Numbers)

Problem:

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 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) {
return sum(root, 0);
}
int sum(TreeNode* root, int n){
if(!root) return 0;
n = 10 * n + root->val;
if(!root->left && !root->right)
return n;
return sum(root->left, n) + sum(root->right, n);
}
};