Eventually found some time to fill in the gaps again. Day 20 took a while but eventually got a depth first solution that runs in around 2 seconds. I suppose I could try and do something fancier to speed things up, but meh.
Solutions here as usual: https://gist.github.com/wence-/7d2a722fba29c94149a75beebfd5333c
The trick is to find the four corners first - which you can do by looking for the four tiles with two unique edges.
Then for part 2 you only have to check two (or four) orientations of four tiles as the starting point.
@grams started
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Eventually found some time to fill in the gaps again. Day 20 took a while but eventually got a depth first solution that runs in around 2 seconds. I suppose I could try and do something fancier to speed things up, but meh.
Solutions here as usual: https://gist.github.com/wence-/7d2a722fba29c94149a75beebfd5333c