Minimum Cost For Tickets Python Solution

lcpy gen -n 983   # by problem number
lcpy gen -s minimum_cost_for_tickets   # by problem name

Input: days = [1,4,6,7,8,20], costs = [2,7,15]
Output: 11
Explanation: For example, here is one way to buy passes that lets you travel your travel plan:
On day 1, you bought a 1-day pass for costs[0] = $2, which covered day 1.
On day 3, you bought a 7-day pass for costs[1] = $7, which covered days 3, 4, ..., 9.
On day 20, you bought a 1-day pass for costs[0] = $2, which covered day 20.
In total, you spent $11 and covered all the days of your travel.

Input: days = [1,2,3,4,5,6,7,8,9,10,30,31], costs = [2,7,15]
Output: 17
Explanation: For example, here is one way to buy passes that lets you travel your travel plan:
On day 1, you bought a 30-day pass for costs[2] = $15 which covered days 1, 2, ..., 30.
On day 31, you bought a 1-day pass for costs[0] = $2 which covered day 31.
In total, you spent $17 and covered all the days of your travel.

class Solution:
    # Time: O(D) where D is the last travel day
    # Space: O(D)
    def min_cost_tickets(self, days: list[int], costs: list[int]) -> int:
        dayset = set(days)
        last = days[-1]
        dp = [0] * (last + 1)
        for day in range(1, last + 1):
            if day not in dayset:
                dp[day] = dp[day - 1]
            else:
                dp[day] = min(
                    dp[day - 1] + costs[0],
                    dp[max(day - 7, 0)] + costs[1],
                    dp[max(day - 30, 0)] + costs[2],
                )
        return dp[last]