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path: root/23_2021.py
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import re
import functools


def run(filename):
    inp = re.findall(r"[A-Z]+", open(filename).read())

    def solve(part2=False):
        A = [inp[0], inp[4]] if not part2 else [inp[0], "D", "D", inp[4]]
        B = [inp[1], inp[5]] if not part2 else [inp[1], "C", "B", inp[5]]
        C = [inp[2], inp[6]] if not part2 else [inp[2], "B", "A", inp[6]]
        D = [inp[3], inp[7]] if not part2 else [inp[3], "A", "C", inp[7]]
        well_len = 3 if not part2 else 5
        b = tuple([*A, "A", *B, "B", *C, "C", *D, "D"])
        t = tuple(["E" for i in range(11)])
        cost = {"A": 1, "B": 10, "C": 100, "D": 1000}
        botTop = {"A": 2, "B": 4, "C": 6, "D": 8}

        @functools.lru_cache(None)
        def moveTop(top, i, j):
            return all(top[k] == "E" for k in range(min(i, j), max(i, j) + 1) if k != i)

        def frontBot(bot):
            for c, i, j in [
                ("A", 0, well_len - 1),
                ("B", well_len, well_len * 2 - 1),
                ("C", well_len * 2, well_len * 3 - 1),
                ("D", well_len * 3, well_len * 4 - 1),
            ]:
                for k in range(i, j):
                    if bot[k] != "E":
                        if not safeBot(bot, c):
                            yield (botTop[c], k)
                        break

        def safeBot(bot, char):
            return all(
                k == char or k == "E"
                for k in bot[
                    well_len * botTop[char] // 2
                    - well_len : well_len * botTop[char] // 2
                ]
            )

        @functools.lru_cache(None)
        def brute(bot, top):
            if part2 and bot == (
                "A",
                "A",
                "A",
                "A",
                "A",
                "B",
                "B",
                "B",
                "B",
                "B",
                "C",
                "C",
                "C",
                "C",
                "C",
                "D",
                "D",
                "D",
                "D",
                "D",
            ):
                return 0
            if not part2 and bot == (
                "A",
                "A",
                "A",
                "B",
                "B",
                "B",
                "C",
                "C",
                "C",
                "D",
                "D",
                "D",
            ):
                return 0
            for i in range(len(top)):
                char = top[i]
                if char == "E":
                    continue
                j = botTop[char]
                if j and moveTop(top, i, j) and safeBot(bot, char):
                    idx = (
                        well_len * botTop[char] // 2
                        - well_len
                        + bot[
                            well_len * botTop[char] // 2
                            - well_len : well_len * botTop[char] // 2
                        ].index(char)
                        - 1
                    )
                    return cost[char] * (abs(j - i) + (idx % well_len) + 1) + brute(
                        bot[:idx] + tuple(top[i]) + bot[idx + 1 :],
                        top[:i] + tuple("E") + top[i + 1 :],
                    )
            ans = float("inf")
            moves = 0
            for c, i in frontBot(bot):
                for j in range(len(top)):
                    if j in [2, 4, 6, 8] or top[j] != "E" or not moveTop(top, c, j):
                        continue
                    moves += 1
                    ans = min(
                        ans,
                        cost[bot[i]] * (i % well_len + 1 + abs(c - j))
                        + brute(
                            bot[:i] + tuple("E") + bot[i + 1 :],
                            top[:j] + tuple(bot[i]) + top[j + 1 :],
                        ),
                    )
            if moves == 0:
                return float("inf")
            else:
                return ans

        print(brute(b, t))

    solve(part2=False)
    solve(part2=True)


run("day23data.txt")