32 lines
1.1 KiB
Markdown
32 lines
1.1 KiB
Markdown
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---
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title: "Advent of Code 2021 - Day 16"
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date: 2021-12-18T01:44:09+01:00
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year: 2021
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day: 16
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stars: 0
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---
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Today's challenge is [here](https://adventofcode.com/2021/day/16).
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My first attempt at solving this puzzle was to use a library called [construct](https://pypi.org/project/construct/) to parse the data, however it turned out to be too hard for me xD
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I managed to create a parser for the literals:
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```python
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literal = Bitwise(Aligned(8, Struct(
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"version" / BitsInteger(3),
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"type" / Const(0b100, BitsInteger(3)),
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"sequence" / RepeatUntil(
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lambda x, _, __: x.flag == 0,
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Struct(
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"flag" / Flag,
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"data" / Nibble,
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),
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),
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"value" / Computed(lambda ctx: reduce(lambda acc, n: (acc << 4) + n.data, ctx.sequence, 0)),
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)))
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assert(literal.parse(b"\xD2\xFE\x28").value == 2021)
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```
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This does work as excepted, but given that the entire problem is a tree of structures, I might just write a bunch of functions to parse the data instead. In construct the recursion has to be done by using `LazyBound` as far as I can tell, which doesn't really work with `Bitwise`.
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