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.

Solution: 1. Recursion (add to sum when reaching the leaf).
2. Iterative solution.

 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 sumNumbers(TreeNode *root) {
13         int sum = 0;
14         sumNumberRe(root, 0, sum);
15         return sum;
16     }
17     
18     void sumNumberRe(TreeNode* root, int num, int &sum)
19     {
20         if(!root) return;
21         num = num * 10 + root->val;
22         if(!root->left && !root->right) {
23             sum += num;
24         }
25         sumNumberRe(root->left, num, sum);
26         sumNumberRe(root->right, num, sum);
27     }
28 };

 

posted @ 2014-04-13 06:46  beehard  阅读(131)  评论(0)    收藏  举报