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

.

/**
* 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;
void depthSearch(TreeNode *root, int num) {
if(root->left == NULL && root->right == NULL) sum += num;
if(root->left) depthSearch(root->left, num * 10 + root->left->val);
if(root->right) depthSearch(root->right, num * 10 + root->right->val);
}
int sumNumbers(TreeNode *root) {
if(root == NULL) return 0;
depthSearch(root, root->val);
return sum;
}
};