202023.py

input = [9, 1, 6, 4, 3, 8, 2, 7, 5]


def fast_dic(cups, steps):  # non-rotated dictionary:  {cup: nextcup, ... }
    current = cups[0]
    mn, mx = min(cups), max(cups)
    carousel = dict(zip(cups, cups[1:] + [cups[0]]))

    for _ in range(steps):
        xyz = [carousel[current]]
        xyz.append(carousel[xyz[0]])
        xyz.append(carousel[xyz[-1]])
        dest = current - 1
        while dest < mn or dest in xyz:
            dest -= 1
            if dest < mn:
                dest = mx
        carousel[current] = carousel[xyz[-1]]
        carousel[xyz[-1]] = carousel[dest]
        carousel[dest] = xyz[0]
        current = carousel[current]
    return carousel


cups = fast_dic(input.copy(), 100)
labels = [cups[1]]
while labels[-1] != 1:
    labels.append(cups[labels[-1]])
print("Part One:", "".join([str(c) for c in labels[:-1]]))

cups = fast_dic(input.copy() + list(range(9 + 1, 1_000_001)), 10_000_000)
c1 = cups[1]
c2 = cups[c1]
print("Part Two:", c1 * c2)