Interesting. I think one of the main benefits of AoC is it tends to teach you things. So I would have gotten stuck, read peoples answers on the subreddit the ne

Interesting. I think one of the main benefits of AoC is it tends to teach you things. So I would have gotten stuck, read peoples answers on the subreddit the next day, and the problem would have stuck in my memory as one that taught me something new. I also wouldn't consider knowing properties of the GCD to be a "random math concept". It shows up in a reasonably large number of contexts. For example, in public key cryptography. A specific case is that at one point someone realized they could just collect hundreds of millions of RSA public keys and crack low entropy ones by checking for common divisors. Doing this naively by checking each pair would have been very costly, but they used properties of the GCD to massively reduce the cost by pooling keys [1]. [1]: Page 7 of https://www.quintessencelabs.com/wp-content/uploads/2020/03/Keyfactor-Research-Report-Factoring-RSA-Keys-in-the-IoT-Era.pdf https://www.quintessencelabs.com/wp-content/uploads/2020/03/...