983. Minimum Cost For Tickets - LeetCode Solution

class Solution:
    def mincostTickets(self, days: List[int], costs: List[int]) -> int:
        dayset = set(days)
        du = [1, 7, 30]

        @lru_cache(None)
        def dp(i):
            if i > 365:
                return 0
            elif i in dayset:
                return min(dp(i + d) + c
                           for c, d in zip(costs, du))
            else:
                return dp(i + 1)

        return dp(1)