advent-of-code/2016/d21/ex2/ex2.py

101 lines
3.1 KiB
Python
Executable file

#!/usr/bin/env python
import enum
import sys
from typing import NamedTuple
class Op(enum.StrEnum):
SWAP_POSITION = "swap position"
SWAP_LETTER = "swap letter"
ROTATE_LEFT = "rotate left"
ROTATE_RIGHT = "rotate right"
ROTATE_BASED = "rotate based"
REVERSE_POSITION = "reverse positions"
MOVE_POSITION = "move position"
class Instruction(NamedTuple):
op: Op
x: str
y: str | None
@classmethod
def from_str(cls, input: str) -> "Instruction":
split_input = input.split()
op = Op(" ".join(split_input[:2]))
x: str
y: str | None
match op:
case Op.ROTATE_LEFT | Op.ROTATE_RIGHT:
x, y = split_input[2], None
case Op.ROTATE_BASED:
x, y = split_input[-1], None
case _:
x, y = split_input[2], split_input[-1]
return cls(op, x, y)
def undo(self, password: str) -> str:
letters = list(password)
match self.op:
case Op.SWAP_POSITION:
assert self.y is not None # Sanity check
x, y = int(self.x), int(self.y)
letters[x], letters[y] = letters[y], letters[x]
case Op.SWAP_LETTER:
assert self.y is not None # Sanity check
x, y = letters.index(self.x), letters.index(self.y)
letters[x], letters[y] = letters[y], letters[x]
case Op.ROTATE_LEFT:
x = int(self.x)
x %= len(letters)
letters = letters[-x:] + letters[:-x]
case Op.ROTATE_RIGHT:
x = int(self.x)
x %= len(letters)
letters = letters[x:] + letters[:x]
case Op.ROTATE_BASED:
# original: 0 1 2 3 4 5 6 7
# result: 1 3 5 7 2 4 6 0
# rotation: 1 2 3 4 6 7 0 1
x = {
1: 1,
3: 2,
5: 3,
7: 4,
2: 6,
4: 7,
6: 0,
0: 1,
}[letters.index(self.x)]
letters = letters[x:] + letters[:x]
case Op.REVERSE_POSITION:
assert self.y is not None # Sanity check
x, y = int(self.x), int(self.y)
letters[x : y + 1] = letters[x : y + 1][::-1]
case Op.MOVE_POSITION:
assert self.y is not None # Sanity check
x, y = int(self.x), int(self.y)
letter = letters.pop(y)
letters.insert(x, letter)
return "".join(letters)
def solve(input: str) -> str:
def parse(input: str) -> list[Instruction]:
return [Instruction.from_str(line) for line in input.splitlines()]
instructions = parse(input)
password = "fbgdceah"
for instruction in instructions[::-1]:
password = instruction.undo(password)
return password
def main() -> None:
input = sys.stdin.read()
print(solve(input))
if __name__ == "__main__":
main()