90 lines
2.2 KiB
Python
90 lines
2.2 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 enum import StrEnum
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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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class Direction(StrEnum):
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UP = "U"
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DOWN = "D"
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LEFT = "L"
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RIGHT = "R"
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def apply(self, pos: Point, n: int = 1) -> Point:
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DIRECTIONS = {
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"U": Point(-1, 0),
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"D": Point(1, 0),
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"L": Point(0, -1),
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"R": Point(0, 1),
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}
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dx, dy = DIRECTIONS[self.value]
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return Point(pos.x + dx * n, pos.y + dy * n)
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DigPlanStep = tuple[Direction, int]
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DigPlan = list[DigPlanStep]
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def solve(input: list[str]) -> int:
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def parse_line(line: str) -> DigPlanStep:
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dir, n, _ = line.split()
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return Direction(dir), int(n)
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def parse(input: list[str]) -> DigPlan:
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return list(map(parse_line, input))
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def dig_trench(plan: DigPlan) -> list[Point]:
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points = [Point(0, 0)]
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for direction, n in plan:
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points.append(direction.apply(points[-1], n))
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# The trench should loop back to the start, make sure we don't count it twice
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if points[-1] == Point(0, 0):
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del points[-1]
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return points
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def lagoon_volume(trench: list[Point]) -> int:
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def shoelace_area(points: list[Point]) -> int:
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# Must be integer because pipes follow the grid, and can't cut squares in half
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return abs(
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sum(
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(points[i - 1].x * points[i].y) - (points[i].x * points[i - 1].y)
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for i in range(len(points))
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)
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// 2
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)
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def perimeter(points: list[Point]) -> int:
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res = 0
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for p, n in itertools.pairwise(itertools.chain(points, [points[0]])):
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res += abs(n.x - p.x) + abs(n.y - p.y)
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return res
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area = shoelace_area(trench)
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trench_points = perimeter(trench)
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interior_points = area - trench_points // 2 + 1
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return interior_points + trench_points
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plan = parse(input)
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trench = dig_trench(plan)
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return lagoon_volume(list(trench))
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def main() -> None:
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input = sys.stdin.read().splitlines()
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print(solve(input))
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if __name__ == "__main__":
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main()
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