[Leetcode] [tree] [Sum root to leaf numbers]

A very simple question, similar to path sum.

 1 /** 2  * Definition for binary tree 3  * struct TreeNode { 4  *     int val; 5  *     TreeNode *left; 6  *     TreeNode *right; 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} 8  * }; 9  */10 class Solution {11 public:12     void sum(TreeNode *root, int now, int &res) {13         if (root == NULL) {14             return;15         }16         now = now * 10 + root->val;17         if (root->left == NULL && root->right == NULL) {18             res += now;19         }20         sum(root->left, now, res);21         sum(root->right, now, res);22     }23     int sumNumbers(TreeNode *root) {24         int res = 0;25         sum(root, 0, res);26         return res;27     }28 };

However, after reading the problem solution, I found that the solution is better than my algorithm! Learn now!

 1 /** 2  * Definition for binary tree 3  * struct TreeNode { 4  *     int val; 5  *     TreeNode *left; 6  *     TreeNode *right; 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} 8  * }; 9  */10 class Solution {11 public:12     int sum(TreeNode *root, int now) {13         if (root == NULL) {14             return 0;15         }16         now = now * 10 + root->val;17         if (root->left == NULL && root->right == NULL) {18             return now;19         }20         return sum(root->left, now) + sum(root->right, now);21     }22     int sumNumbers(TreeNode *root) {23         return sum(root, 0);24     }25 };

Fewer parameters, shorter code!