[LintCode] 535. House Robber III

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

Example1

Input:  {3,2,3,#,3,#,1}
Output: 7
Explanation:
Maximum amount of money the thief can rob = 3 + 3 + 1 = 7.
  3
 / 
2   3
     
  3   1

Example2

Input:  {3,4,5,1,3,#,1}
Output: 9
Explanation:
Maximum amount of money the thief can rob = 4 + 5 = 9.
    3
   / 
  4   5
 /     
1   3   1

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */

public class Solution {
    /**
     * @param root: The root of binary tree.
     * @return: The maximum amount of money you can rob tonight
     */
    public int houseRobber3(TreeNode root) {
        // write your code here
        ResType res = helper(root);
        return Math.max(res.rob, res.notRob);
    }
    
    private ResType helper(TreeNode root) {
        if (root == null) {
            return new ResType();
        }
        ResType cur = new ResType();
        ResType left = helper(root.left);
        ResType right = helper(root.right);
        cur.rob = left.notRob + right.notRob + root.val;
        cur.notRob = Math.max(left.rob, left.notRob) + Math.max(right.rob, right.notRob);
        return cur;
    }
}

class ResType {
    int rob;
    int notRob;
}