📄 Description

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that adjacent houses have security systems 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 = [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 2:

Input: nums = [2,7,9,3,1]
Output: 12
Explanation: Rob house 1 (money = 2), rob house 3 (money = 9) and rob house 5 (money = 1).
Total amount you can rob = 2 + 9 + 1 = 12.

Constraints:

• 1 <= nums.length <= 100
• 0 <= nums[i] <= 400

💻 My Submission - Recursion

class Solution:
    def rob(self, nums: List[int]) -> int:
        house=defaultdict(int)
        def cur_rob(i):
            if i>=len(nums): return 0
            if i in house[i]: return house[i]
            # if house[i]: return house[i]
            first=cur_rob(i+2)+nums[i]
            second=cur_rob(i+1)
            house[i]=max(first, second)
            return house[i]
        
        return cur_rob(0)

🚩 Other Solution - Tabulation

class Solution:
    def rob(self, nums: List[int]) -> int:
        if not nums:
            return 0
        
        dp = {}
        dp[0] = 0
        dp[1] = nums[0]
        
        for i in range(2, len(nums) + 1):
            dp[i] = max(dp[i - 1], dp[i - 2] + nums[i - 1])
        return dp[len(nums)]

💡 What I learned

Using dict vs dictionary for Memoization

# Using list
dp=[0]*len(nums)
# Using dictionary
dp=defaultdict(int)

❓ Question

What' the difference between below two lines..?

if i in house[i]: return house[i]            

and

if house[i]: return house[i]

References

• https://leetcode.com/problems/house-robber/
• https://leetcode.com/problems/house-robber/discuss/55696/Python-solution-3-lines.
• https://stackoverflow.com/questions/8725673/multiple-assignment-and-evaluation-order-in-python