111 lines
2.8 KiB
Python
111 lines
2.8 KiB
Python
from collections.abc import Iterable
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from functools import reduce
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from itertools import product
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from pathlib import Path
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from typing import NamedTuple
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class Point(NamedTuple):
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x: int
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y: int
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def iter_adjacent(self, wrap=False) -> Iterable["Point"]:
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for offset in product((1, 0, -1), (1, 0, -1)):
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adj = Point(self.x + offset[0], self.y + offset[1])
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if adj == self:
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continue
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if not wrap and (adj.x < 0 or adj.y < 0):
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continue
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yield adj
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def __str__(self) -> str:
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return f"Point({self.x}, {self.y})"
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def is_symbol(v: str) -> bool:
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return not v.isnumeric() and v != "."
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def read_part(grid: list[str], point: Point) -> tuple[Point, int]:
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points = [point]
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num = grid[point.y][point.x]
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if not num.isnumeric():
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raise ValueError(f"Can't read a part because {num}@{point} is not a number")
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row = grid[point.y]
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x = point.x - 1
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while x >= 0 and row[x].isnumeric():
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num = row[x] + num
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points.append(Point(x, point.y))
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x -= 1
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left_point = Point(x, point.y)
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x = point.x + 1
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while x < len(row) and row[x].isnumeric():
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num = num + row[x]
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points.append(Point(x, point.y))
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x += 1
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print(f"Part {num}@{left_point} for {point}")
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return left_point, int(num)
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def find_parts(grid: list[str], point: Point) -> dict[Point, int]:
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parts: dict[Point, int] = {}
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for adjacent in point.iter_adjacent():
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if adjacent.y >= len(grid) or adjacent.x >= len(grid[adjacent.y]):
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continue
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if grid[adjacent.y][adjacent.x].isnumeric():
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point, part_num = read_part(grid, adjacent)
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parts[point] = part_num
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return parts
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def part1(input: Path) -> int:
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with input.open() as f:
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grid = [line.strip() for line in f]
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all_parts: dict[Point, int] = {}
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for y, row in enumerate(grid):
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for x, cell in enumerate(row):
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p = Point(x, y)
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if is_symbol(cell):
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parts = find_parts(grid, p)
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all_parts.update(parts)
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return sum(all_parts.values())
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def part2(input: Path) -> int:
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with input.open() as f:
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grid = [line.strip() for line in f]
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total = 0
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for y, row in enumerate(grid):
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for x, cell in enumerate(row):
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p = Point(x, y)
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if cell != "*":
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continue
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parts = find_parts(grid, p)
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if len(parts) != 2:
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continue
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gear_ratio = reduce(lambda x, y: x*y, parts.values(), 1)
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total += gear_ratio
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return total
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if __name__ == "__main__":
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result1 = part1(Path("./input.txt"))
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print("part 1", result1)
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result2 = part2(Path("./input.txt"))
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print("part 2", result2)
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