House Robber II

Author: anantkaushik

213-house-robber-ii.py

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+"""
+Problem Link: https://leetcode.com/problems/house-robber-ii/
+
+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.
+
+Example 1:
+Input: nums = [2,3,2]
+Output: 3
+Explanation: You cannot rob house 1 (money = 2) and then rob house 3 (money = 2), 
+because they are adjacent houses.
+
+Example 2:
+Input: nums = [1,2,3,1]
+Output: 4
+Explanation: Rob house 1 (money = 1) and then rob house 3 (money = 3).
+Total amount you can rob = 1 + 3 = 4.
+
+Example 3:
+Input: nums = [1,2,3]
+Output: 3
+ 
+Constraints:
+
+1 <= nums.length <= 100
+0 <= nums[i] <= 1000
+"""
+class Solution:
+ def rob(self, nums: List[int]) -> int:
+ if len(nums) == 1:
+ return nums[0]
+ 
+ sl_house = nums[0]
+ l_house = max(nums[0], nums[1])
+ sl_house_exculding_first = 0
+ l_house_exculding_first = nums[1]
+ 
+ for index in range(2, len(nums)):
+ if index < len(nums) - 1:
+ sl_house, l_house = l_house, max(l_house, nums[index] + sl_house)
+ 
+ sl_house_exculding_first, l_house_exculding_first = l_house_exculding_first, max(l_house_exculding_first, nums[index] + sl_house_exculding_first)
+ 
+ return max(l_house, l_house_exculding_first)
+
+# Two Pass
+class Solution1:
+ def rob(self, nums: List[int]) -> int:
+ if len(nums) == 1:
+ return nums[0]
+ 
+ second_last_house = nums[0]
+ last_house = max(nums[0], nums[1])
+ 
+ for index in range(2, len(nums)-1):
+ second_last_house, last_house = last_house, max(last_house, nums[index] + second_last_house)
+ 
+ res = last_house
+ # excluding first
+ second_last_house = 0
+ last_house = nums[1]
+ 
+ for index in range(2, len(nums)):
+ second_last_house, last_house = last_house, max(last_house, nums[index] + second_last_house)
+ 
+ return max(res, last_house)
+# Memo
+class Solution2:
+ def rob(self, nums: List[int]) -> int:
+ if len(nums) == 1:
+ return nums[0]
+ 
+ return max(self.helper(nums, len(nums)-1, False, {}), self.helper(nums, len(nums)-2, True, {}))
+ 
+ def helper(self, nums, index, include_first, memo):
+ if index < 0 or (index == 0 and not include_first):
+ return 0
+ 
+ if index not in memo:
+ memo[index] = max(self.helper(nums, index-1, include_first, memo), nums[index] + self.helper(nums, index - 2, include_first, memo))
+ 
+ return memo[index]
+
+
+# TLE
+class Solution3:
+ def rob(self, nums: List[int]) -> int:
+ if len(nums) == 1:
+ return nums[0]
+ 
+ return max(self.helper(nums, len(nums)-1), self.helper(nums, len(nums)-2, True))
+ 
+ def helper(self, nums, index, include_first=False):
+ if index < 0 or (index == 0 and not include_first):
+ return 0
+ 
+ return max(self.helper(nums, index-1, include_first), nums[index] + self.helper(nums, index - 2, include_first))