79 lines
2.2 KiB
Python
79 lines
2.2 KiB
Python
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#!/usr/bin/env python3
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import sys
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import dataclasses
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import re
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from typing import Sequence, Set, Tuple
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from copy import deepcopy
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FOLD_RE = re.compile(r"fold along (?P<dir>[xy])=(?P<off>[0-9]+)")
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Point = Tuple[int, int]
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@dataclasses.dataclass
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class Fold:
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direction: str
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offset: int
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@staticmethod
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def from_str(s: str) -> "Fold":
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match = FOLD_RE.match(s)
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assert match
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return Fold(match["dir"], int(match["off"]))
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class Grid:
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def __init__(self, points: Set[Point]):
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self.rows = max(y for x, y in points) + 1
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self.cols = max(x for x, y in points) + 1
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self.points = points
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def apply_fold(self, fold: Fold):
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if fold.direction == "y":
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# Find all points that are below this line
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below = {(x, y) for x, y in self.points if y > fold.offset}
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# Find their new positions and then remove the old ones
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self.points -= below
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self.points |= {(x, self.rows - y - 1) for (x, y) in below}
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self.rows //= 2
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else:
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# Find all points that are to the right of this line
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right = {(x, y) for x, y in self.points if x > fold.offset}
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# Find their new positions and then remove the old ones
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self.points -= right
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self.points |= {(self.cols - x - 1, y) for (x, y) in right}
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self.cols //= 2
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def display(self) -> Sequence[str]:
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grid = [["." for _ in range(self.cols)] for _ in range(self.rows)]
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for x, y in self.points:
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grid[y][x] = "#"
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return ["".join(line) for line in grid]
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def part1(grid: Grid, folds: Sequence[Fold]):
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grid = deepcopy(grid)
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grid.apply_fold(folds[0])
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print(len(grid.points))
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def part2(grid: Grid, folds: Sequence[Fold]):
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for fold in folds:
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grid.apply_fold(fold)
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print("\n".join(grid.display()))
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points_str, folds_str = sys.stdin.read().split("\n\n")
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points = {
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(int(a), int(b))
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for a, b in map(lambda line: line.split(","), points_str.split("\n"))
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}
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grid = Grid(points)
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folds = [Fold.from_str(line) for line in folds_str.split("\n")]
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print("Part 1")
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part1(grid, folds)
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print("Part 2")
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part2(grid, folds)
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