[Leetcode 39] 129 Sum Root to Leaf Numbers

Problem:

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.

Analysis:

Simple tree DFS problem.

Code:

 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         // Start typing your C/C++ solution below
14         // DO NOT write int main() function
15         if (root == NULL) return 0;
16         
17         int pathSum = 0, total = 0;
18         helper(root, pathSum, total);
19         
20         return total;
21     }
22     
23     int helper(TreeNode *node, int pathSum, int& total) {
24         if (node->left==NULL && node->right==NULL) {
25             total += pathSum*10 + node->val;
26         }
27         
28         pathSum = pathSum*10 + node->val;
29         if(node->left != NULL)
30             helper(node->left, pathSum, total);
31             
32         if (node->right != NULL)
33             helper(node->right, pathSum, total);
34     }
35     
36 };

View Code

Attention: