72 lines
2.1 KiB
Python
72 lines
2.1 KiB
Python
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#!/usr/bin/env python
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import itertools
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import sys
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from copy import deepcopy
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from typing import Iterable, List, Tuple, cast
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Paper = List[List[bool]]
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Instruction = Tuple[str, int]
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def solve(input: List[str]) -> int:
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def transpose(paper: Paper) -> Paper:
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return cast(Paper, list(zip(*paper)))
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def fold_along_y(paper: Paper, y: int) -> Paper:
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assert not any(paper[y]) # Sanity check
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assert y >= len(paper) // 2 # Ensure that we can actually fold the paper
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paper = deepcopy(paper)
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for i, j in zip(itertools.count(y, -1), range(y, len(paper))):
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paper[i] = [(dot_i or dot_j) for dot_i, dot_j in zip(paper[i], paper[j])]
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paper = paper[:y]
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return paper
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def fold_along_x(paper: Paper, x: int) -> Paper:
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return transpose(fold_along_y(transpose(paper), x))
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def do_folds(paper: Paper, instructions: Iterable[Instruction]) -> Paper:
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for axis, n in instructions:
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if axis == "x":
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paper = fold_along_x(paper, n)
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elif axis == "y":
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paper = fold_along_y(paper, n)
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else:
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assert False # Sanity check
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return paper
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def parse() -> Tuple[Paper, List[Instruction]]:
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paper_part = itertools.takewhile(lambda s: s != "", input)
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fold_part = itertools.islice(
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itertools.dropwhile(lambda s: s != "", input), 1, None
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)
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points = {(int(x), int(y)) for x, y in map(lambda s: s.split(","), paper_part)}
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folds = [
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(axis[-1], int(n)) for axis, n in map(lambda s: s.split("="), fold_part)
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]
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width, height = max(p[0] for p in points), max(p[1] for p in points)
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paper = [
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[(x, y) in points for x in range(width + 1)] for y in range(height + 1)
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]
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return paper, folds
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paper, instructions = parse()
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return sum(itertools.chain.from_iterable(do_folds(paper, instructions[:1])))
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def main() -> None:
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input = [line.strip() for line in sys.stdin.readlines()]
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print(solve(input))
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if __name__ == "__main__":
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main()
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