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Multiple States IV

Description

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.

https://leetcode.com/problems/house-robber-iii/description/

Example I:

Input: [3,2,3,null,3,null,1]

     3
    / \
   2   3
    \   \ 
     3   1

Output: 7 
Explanation: Maximum amount of money the thief can rob = 3 + 3 + 1 = 7.

Example II:

Input: [3,4,5,1,3,null,1]

     3
    / \
   4   5
  / \   \ 
 1   3   1

Output: 9
Explanation: Maximum amount of money the thief can rob = 4 + 5 = 9.

Questions

Transform Function

int[]{rob, notrob] = new int[]{left.notrob + right.notrob + cur.val, Math.max(left.notrob, left.rob) + Math.(right.notrob, right.rob)

Solution I

class Solution {
    public int rob(TreeNode root) {
        int[] res = helper(root);
        return Math.max(res[0], res[1]);
    }

    int[] helper(TreeNode root) {
        if(root == null) return new int[]{0, 0};
        int[] left = helper(root.left);
        int[] right = helper(root.right);
        int rob = left[1] + right[1] + root.val;
        int notrob = Math.max(left[0], left[1]) + Math.max(right[0], right[1]);
        return new int[]{rob, notrob};
    }
}