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Friday, February 22, 2013

[LeetCode] Sum Root to Leaf Numbers, Solution


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.
» Solve this problem


[Thoughts]
Recursion. Similar as [LeetCode] Binary Tree Maximum Path Sum Solution, the difference here is only adding a track variable to sum all the paths.

[Code]
1:       int sumNumbers(TreeNode *root) {  
2:            int sum=0, path =0;            
3:            GenerateSum(root, sum, path);  
4:            return sum;  
5:       }  
6:       void GenerateSum(TreeNode *root, int& sum, int path)  
7:       {  
8:            if(root == NULL) return;      
9:            path = path*10 +root->val;  
10:            if(root->left == NULL && root->right == NULL)  
11:            {  
12:                 sum+=path;  
13:                 return;  
14:            }  
15:            GenerateSum(root->left, sum, path);  
16:            GenerateSum(root->right, sum, path);  
17:       }  










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