aoc/2020/23/23.py
2020-12-23 09:07:12 -06:00

45 lines
1.1 KiB
Python

def read_file():
with open("input.txt","r") as f:
return list(map(int,list(f.read())))
def play(cups, rounds):
current = cups[0]
next_cup = {c:n for c, n in zip(cups, cups[1:] + [cups[0]])}
for _ in range(rounds):
# pickup next 3 cups
c1 = next_cup[current]
c2 = next_cup[c1]
c3 = next_cup[c2]
# select a destination cup (-1 until found, wraps around)
destination = current - 1 if current > 1 else len(cups)
while destination in [c1, c2, c3]:
destination = destination - 1 if destination > 1 else len(cups)
# add cups back
next_cup[current] = next_cup[c3]
next_cup[c3] = next_cup[destination]
next_cup[destination] = c1
# select a new current cup (next)
current = next_cup[current]
# rebuild cups from next_cup
cup = 1
new_cups = []
for _ in range(len(cups)):
cup = next_cup[cup]
new_cups.append(cup)
return new_cups
def part1(cups):
cups = play(cups, 100)
return "".join(str(c) for c in cups[:-1])
def part2(cups):
cups += list(range(10,1_000_001))
cups = play(cups,10_000_000)
return cups[0] * cups[1]
def main():
cups = read_file()
print(part1(cups), part2(cups))
if __name__ == "__main__":
main()