LeetCode 337. House Robber III

 1 /**
 2  * Definition for a binary tree node.
 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 helpRob(TreeNode* root, int& in, int& out){
13         if(!root) return;
14         int lin = 0, lout = 0, rin = 0, rout = 0;
15         helpRob(root->left, lin, lout);
16         helpRob(root->right, rin, rout);
17         in = lout + rout + root->val;
18         out = max(lin, lout) + max(rin, rout);
19     }
20     int rob(TreeNode* root) {
21         if(!root) return 0;
22         int in = 0, out = 0;
23         helpRob(root, in, out);
24         return max(in, out);
25     }
26 };