LC213 - House Robber II

Problem

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed. All houses at this place are arranged in a circle. That means the first house is the neighbor of the last one. Meanwhile, adjacent houses have a security system connected, and it will automatically contact the police if two adjacent houses were broken into on the same night.

Given an integer array nums representing the amount of money of each house, return the maximum amount of money you can rob tonight without alerting the police.

Solution

Dynamic Programming

Expand on the original House Robber problem by handling the edge cases of when the ends are adjacent and for an empty subarray. Time complexity is $O(n)$, and no extra space is used so $O(1)$ space.

def rob(self, nums: List[int]) -> int:
	# Handle edge case of when ends are adjacent and if   subarray empty
	return max(nums[0], self.robMax(nums[1:]), self.robMax(nums[:-1]))

def robMax(self, nums):
	rob1 = 0
	rob2 = 0
	
	for n in nums:
		maxRob = max(n + rob1, rob2)
		rob1 = rob2
		rob2 = maxRob
	
	return rob2