Advent of Code 2021 day 21 part 2

AoC_2021_21_2.py

import re
from collections import defaultdict

DISPATCHES = {3: 1, 4: 3, 5: 6, 6: 7, 7: 6, 8: 3, 9: 1}

inp = open("input_21.txt").read().strip()
pos = tuple(map(lambda x: int(x) - 1, re.findall(r": (\d+)", inp)))
ucnts = defaultdict(int)
ucnts[((pos[0], 0), (pos[1], 0))] = 1  # key: ((pos, score), (pos, score))
wins = [0, 0]
pid = 0  # player id

while ucnts:
    tmp = defaultdict(int)
    for key, cnt in ucnts.items():
        pos, score = key[pid]
        for delta, n in DISPATCHES.items():
            newpos = (pos + delta) % 10
            newscore = score + newpos + 1
            newcnt = cnt * n
            if newscore >= 21:
                wins[pid] += newcnt
            else:
                if pid == 0:
                    tmp[((newpos, newscore), key[1])] += newcnt
                else:
                    tmp[(key[0], (newpos, newscore))] += newcnt
    ucnts = tmp
    pid = 1 - pid

print(max(wins))