I don’t seem to be able to edit posts any more for some reason. The issue I have is that the 1712th block is a J shape that comes to rest atop a cross shape. For some reason mine is resting atop the vertical bit of the cross rather than the horizontal bit. I must have an issue in my shift calculation or my placement of pieces on the board but I can’t find it.
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Nope. Problem is in parsing the input apparently. The horizontal block that lands before the cross is supposed to go R->L->L->L, but for some reason mine is trying to go R->R->R->L. This leads to the following cross block landing on top of that horizontal piece rather than nesting alongside it. Debugging continues.
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Oh for crying out loud. I didn’t trim the input. I thought I’d be clever and convert the “<” and “>” to -1 and 1 by taking their codepoint value (60 and 62) and subtracting 61. But passing the “\n” character created a shift by -51 (which does nothing but throws the cycle out of phase). Trimming the input and my solution now works. Crikey.