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 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) {

int sum=0;
return dfs(root,sum);

}

int  dfs(TreeNode *root,int sum)
{

if(root==NULL) return 0;
if(!root->left&&!root->right)
return sum*10+root->val;

return dfs(root->left,sum*10+root->val)+dfs(root->right,sum*10+root->val);
}
};