advent-of-code/2017-python/solutions/day_16.py

from solutions import BaseSolution


class Solution(BaseSolution):
    input_file = "16.txt"

    def __str__(self):
        return "Day 16: Permutation Promenade"

    def _move(self, programs, m, i):
        l = len(programs)
        if m == "s":
            r = int(i)
            return programs[-r:] + programs[: l - r]
        if m == "x":
            x, y = [int(s) for s in i.split("/")]
            z = programs[x]
            programs[x] = programs[y]
            programs[y] = z
            return programs
        if m == "p":
            xp, yp = i.split("/")
            x = programs.index(xp)
            y = programs.index(yp)
            z = programs[x]
            programs[x] = programs[y]
            programs[y] = z
            return programs

    def _dance(self, programs, moves):
        for m in moves:
            programs = self._move(programs, m[0], m[1:])
        return programs

    def solve(self, puzzle_input, n=16):
        programs = [chr(c) for c in range(97, 97 + n)]
        moves = puzzle_input.split(",")
        return "".join(self._dance(programs, moves))

    def solve_again(self, puzzle_input, n=16):
        moves = puzzle_input.split(",")
        initial = [chr(c) for c in range(97, 97 + n)]
        programs = list(self.solve(puzzle_input))
        dances = 1
        while not programs == initial:
            programs = self._dance(programs, moves)
            dances += 1
        for _ in range(10**9 % dances):
            programs = self._dance(programs, moves)
        return "".join(programs)


if __name__ == "__main__":
    solution = Solution()
    solution.show_results()