21.py

"""--- Day 21: Scrambled Letters and Hash ---"""

def swap(l, i, j):
    l[i], l[j] = l[j], l[i]
    return l

def move(l, i, j):
    t = l.pop(i)
    l.insert(j, t)
    return l

def reverse(l, i, j):
    sub = l[i:j][::-1]
    return l[:i] + sub + l[j:]

def rotate_right(l, n):
    i = n % len(l)
    return l[-i:] + l[:-i]

def rotate_left(l, n):
    i = n % len(l)
    return l[i:] + l[:i]

with open("input/21.txt") as f:
    password = list("abcdefgh")
    for instruction in f:
        cmd = instruction.split()
        if cmd[0] == "swap":
            if cmd[1] == "position":
                password = swap(password, int(cmd[2]), int(cmd[5]))
            else:
                password = swap(password, password.index(cmd[2]), password.index(cmd[5]))
        elif cmd[0] == "reverse":
            password = reverse(password, int(cmd[2]), int(cmd[4]) + 1)
        elif cmd[0] == "rotate":
            if cmd[1] == "left":
                password = rotate_left(password, int(cmd[2]))
            elif cmd[1] == "right":
                password = rotate_right(password, int(cmd[2]))
            else:
                rotations = password.index(cmd[6]) + 1
                if rotations > 4:
                    rotations += 1
                password = rotate_right(password, rotations)
        elif cmd[0] == "move":
            password = move(password, int(cmd[2]), int(cmd[5]))

    print("".join(password))

with open("input/21.txt") as f:
    instructions = f.read().split("\n")
    instructions.reverse()

    password = list("fbgdceah")

    for instruction in instructions[1:]:
        cmd = instruction.split()
        if cmd[0] == "swap":
            if cmd[1] == "position":
                password = swap(password, int(cmd[5]), int(cmd[2]))
            else:
                password = swap(password, password.index(cmd[5]), password.index(cmd[2]))
        elif cmd[0] == "reverse":
            password = reverse(password, int(cmd[2]), int(cmd[4]) + 1)
        elif cmd[0] == "rotate":
            if cmd[1] == "left":
                password = rotate_right(password, int(cmd[2]))
            elif cmd[1] == "right":
                password = rotate_left(password, int(cmd[2]))
            else:
                cur_pos = password.index(cmd[6])
                if cur_pos == 0:
                    rotations = 1
                elif cur_pos == 1:
                    rotations = 1
                elif cur_pos == 2:
                    rotations = 6
                elif cur_pos == 3:
                    rotations = 2
                elif cur_pos == 4:
                    rotations = 7
                elif cur_pos == 5:
                    rotations = 3
                elif cur_pos == 6:
                    rotations = 0
                elif cur_pos == 7:
                    rotations = 4
                password = rotate_left(password, rotations)
        elif cmd[0] == "move":
            password = move(password, int(cmd[5]), int(cmd[2]))
    print("".join(password))