trolley.py

INTERSECTIONS = ["A 2", "A 3", "A 6", "B 4", "B 5", "C 1", "C 3", "D 1", "D 2", "D 4"]


def Letter(intersection):
    return intersection.split()[0]


def Number(intersection):
    return intersection.split()[1]


def tell(part, possible_intersections=INTERSECTIONS):
    return [
        intersection for intersection in possible_intersections if part in intersection
    ]


def know(possible_intersections):
    return len(list(possible_intersections)) == 1


def collision_intersection(possible_intersections=INTERSECTIONS):
    return list(filter(statement1to3, possible_intersections))


def statement1(intersection):
    possible_intersections = tell(Letter(intersection))
    return not know(possible_intersections) and all(
        not know(tell(Number(intersection))) for intersection in possible_intersections
    )


def statement2(intersection):
    at_first = tell(Number(intersection))
    return not know(at_first) and know(filter(statement1, at_first))


def statement3(intersection):
    return know(filter(statement2, tell(Letter(intersection))))


def statement1to3(intersection):
    return (
        statement1(intersection)
        and statement2(intersection)
        and statement3(intersection)
    )