## Monday, July 24, 2017

### [Leetcode] House Robber III, Solution

The thief has found himself a new place for his thievery again. There is only one entrance to this area, called the "root." Besides the root, each house has one and only one parent house. After a tour, the smart thief realized that "all houses in this place forms a binary tree". It will automatically contact the police if two directly-linked houses were broken into on the same night.
Determine the maximum amount of money the thief can rob tonight without alerting the police.
Example 1:
```     3
/ \
2   3
\   \
3   1
```
Maximum amount of money the thief can rob = 3 + 3 + 1 = 7.
Example 2:
```     3
/ \
4   5
/ \   \
1   3   1
```
Maximum amount of money the thief can rob = 4 + 5 = 9.

[Thoughts]

1. root + left_left + left_right + right_left + right_right
2. left + right

[Code]

``````1:    int rob(TreeNode* root) {
2:      if(root == NULL) return 0;
3:
4:      int val = 0;
5:
6:      if(root->left) {
7:        val += rob(root->left->left) + rob(root->left->right);
8:      }
9:
10:      if(root->right) {
11:        val += rob(root->right->left) + rob(root->right->right);
12:      }
13:
14:      return max(root->val + val, rob(root->left) + rob(root->right));
15:    }
``````