pigeon-magnet-solver/pigeon_magnet_solver/helpers.py

from typing import Iterable, TypeVar

T = TypeVar("T")


def _rotate_r(__s: list[T]) -> list[T]:
    return [__s[-1]] + __s[0:-1]


def _valid_rotate(__s: Iterable[str], __c: Iterable[str]) -> bool:
    for sc, cc in zip(__s, __c):
        # can never rotate a "1" onto an "x"
        if sc == "x" and cc == "1":
            return False

    return True


def _fix_exes(__s: Iterable[str], __c: Iterable[str]) -> list[str]:
    result = []

    for sc, cc in zip(__s, __c):
        if sc == "x":
            result.append("x")

        elif cc == "x":
            result.append("0")

        else:
            result.append(cc)

    return result


def rotate_r(__s: list[str]) -> list[str]:
    result = _rotate_r(__s)

    while not _valid_rotate(__s, result):
        result = _rotate_r(result)

    return _fix_exes(__s, result)