【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.

 

class Solution {
public:
    int dfs(TreeNode* root,int sum)
    {
        if(root==NULL) return  0;
        if(root->left==NULL&&root->right==NULL)
            return sum*10+root->val;

        return dfs(root->left,sum*10+root->val)+dfs(root->right,sum*10+root->val);
    }
    int sumNumbers(TreeNode* root) {
        return dfs(root,0);
    }
};