Correct.

Part 1: easy.

Apply part 1 solution to example, works.

Apply part 1 solution to real input, works.

Part 2: hard to very hard.

Apply part 2 solution to example, usually works.

Apply part 2 solution to real input, doesn't work due to time / memory constraints.

But having to look at the input to discover a pattern that isn't explained as part of the instructions always irks me.