aoc-2020/22.py

lines = []

with open("22.input") as f:
    for line in f.readlines():
        lines.append(line.strip())


split_index = lines.index("Player 2:")

d1 = [int(i) for i in lines[1:split_index-1]]
d2 = [int(i) for i in lines[split_index+1:]]

def combat(d1, d2):
    while d1 != [] and d2 != []:
        p1 = d1.pop(0)
        p2 = d2.pop(0)
        if p1 > p2:
            d1.append(p1)
            d1.append(p2)
        else:
            d2.append(p2)
            d2.append(p1)

    return d1 if d1 != [] else d2

def calc_score(win_deck):
    win_deck.reverse()
    score = sum([k * x for (k, x) in zip(win_deck, range(1, len(win_deck) + 1))])
    win_deck.reverse()
    return score

print("Answer 1:", calc_score(combat(list(d1), list(d2))))

def recursive_combat(d1, d2):
    round = 1
    previous_rounds = set()
    while d1 != [] and d2 != []:
        #print("-- Round {} --".format(round))
        #print("Player 1's deck:", d1)
        #print("Player 2's deck:", d2)
        p1 = d1.pop(0)
        p2 = d2.pop(0)
        #print("Player 1 plays:", p1)
        #print("Player 2 plays:", p2)
        if (tuple(d1), tuple(d2)) in previous_rounds:
            return (1, [])
        previous_rounds.add((tuple(d1), tuple(d2)))
        if len(d1) >= p1 and len(d2) >= p2:
            winner, win_deck = recursive_combat(list(d1[0:p1]), list(d2[0:p2]))
        else:
            winner = 1 if p1 > p2 else 2
        #print("Player {} wins round {}".format(winner, round))
        if winner == 1:
            d1 += [p1, p2]
        else:
            d2 += [p2, p1]

    return (1, d1) if d1 != [] else (2, d2)

print("Answer 2:", calc_score(recursive_combat(d1, d2)[1]))