diff --git a/2022/d09/ex2/ex2.py b/2022/d09/ex2/ex2.py new file mode 100755 index 0000000..75124a1 --- /dev/null +++ b/2022/d09/ex2/ex2.py @@ -0,0 +1,96 @@ +#!/usr/bin/env python + +import dataclasses +import enum +import sys +from typing import NamedTuple + + +def sign(n: int) -> int: + if n > 0: + return 1 + elif n < 0: + return -1 + return 0 + + +class Direction(enum.Enum): + UP = "U" + DOWN = "D" + LEFT = "L" + RIGHT = "R" + + +@dataclasses.dataclass +class Move: + dir: Direction + len: int + + @classmethod + def from_input(cls, line: str) -> "Move": + d, l = line.split() + return cls(Direction(d), int(l)) + + +class Point(NamedTuple): + x: int + y: int + + def move(self, direction: Direction) -> "Point": + match direction: + case Direction.UP: + dx, dy = 1, 0 + case Direction.DOWN: + dx, dy = -1, 0 + case Direction.LEFT: + dx, dy = 0, -1 + case Direction.RIGHT: + dx, dy = 0, 1 + return Point(self.x + dx, self.y + dy) + + +@dataclasses.dataclass +class Rope: + points: list[Point] = dataclasses.field(init=False) + _tail_positions: set[Point] = dataclasses.field(init=False) + + def __init__(self, *, length: int = 2) -> None: + assert length > 0 + self.points = [Point(0, 0)] * length + self._tail_positions = {self.points[-1]} + + def move(self, move: Move) -> None: + for _ in range(move.len): + self.points[0] = self.points[0].move(move.dir) + for i in range(1, len(self.points)): + self.points[i] = self.__move_tail(self.points[i - 1], self.points[i]) + self._tail_positions.add(self.points[-1]) + + @staticmethod + def __move_tail(head: Point, tail: Point) -> Point: + delta_x, delta_y = head.x - tail.x, head.y - tail.y + + if abs(delta_x) <= 1 and abs(delta_y) <= 1: + return tail + + dx, dy = sign(delta_x), sign(delta_y) + return Point(tail.x + dx, tail.y + dy) + + +def solve(input: list[str]) -> int: + moves = map(Move.from_input, input) + rope = Rope(length=10) + + for move in moves: + rope.move(move) + + return len(rope._tail_positions) + + +def main() -> None: + input = sys.stdin.read().splitlines() + print(solve(input)) + + +if __name__ == "__main__": + main()