From 128617566fd0d04009e74ec55d197cd41d284c49 Mon Sep 17 00:00:00 2001 From: June McEnroe Date: Sun, 13 Dec 2020 17:10:01 -0500 Subject: Spoiled solve day 13 part 2 I think I might've been close to coming up with this at some point but everyone was acting like it was impossible without knowing "Chinese Remainder Theorem" and I just got pissed off. --- 2020/day13.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to '2020') diff --git a/2020/day13.c b/2020/day13.c index f8c0665..a0e8c98 100644 --- a/2020/day13.c +++ b/2020/day13.c @@ -23,4 +23,14 @@ int main(void) { } } printf("%d\n", bus * min); + long t = 0; + long x = buses[0]; + for (int i = 1; i < len; ++i) { + if (!buses[i]) continue; + while ((t + i) % buses[i]) { + t += x; + } + x *= buses[i]; + } + printf("%ld\n", t); } -- cgit 1.4.1