2018: d10: ex2: add solution

2018/d10/ex2/ex2.py

@@ -0,0 +1,65 @@
+#!/usr/bin/env python
+
+import itertools
+import sys
+from typing import NamedTuple
+
+
+class Point(NamedTuple):
+    x: int
+    y: int
+
+
+class Light(NamedTuple):
+    pos: Point
+    vel: Point
+
+    def at(self, time: int) -> Point:
+        return Point(self.pos.x + self.vel.x * time, self.pos.y + self.vel.y * time)
+
+
+def solve(input: str) -> int:
+    def parse_light(input: str) -> Light:
+        pos, vel = map(lambda s: s.split("=<")[1].removesuffix(">"), input.split("> "))
+        return Light(
+            Point(*map(int, map(str.strip, pos.split(",")))),
+            Point(*map(int, map(str.strip, vel.split(",")))),
+        )
+
+    def parse(input: list[str]) -> list[Light]:
+        return [parse_light(line) for line in input]
+
+    def move_lights(lights: list[Light], time: int) -> set[Point]:
+        return {l.at(time) for l in lights}
+
+    def bbox_size(points: set[Point]) -> int:
+        min_x, max_x = min(p.x for p in points), max(p.x for p in points)
+        min_y, max_y = min(p.y for p in points), max(p.y for p in points)
+        return (max_x - min_x + 1) * (max_y - min_y + 1)
+
+    def write_message(message: set[Point]) -> str:
+        min_x, max_x = min(p.x for p in message), max(p.x for p in message)
+        min_y, max_y = min(p.y for p in message), max(p.y for p in message)
+
+        return "\n".join(
+            "".join(
+                "#" if Point(x, y) in message else "." for x in range(min_x, max_x + 1)
+            )
+            for y in range(min_y, max_y + 1)
+        )
+
+    lights = parse(input.splitlines())
+    max_time = max(
+        map(abs, itertools.chain.from_iterable((l.pos.x, l.pos.y) for l in lights))
+    )
+    time = min(range(max_time), key=lambda t: bbox_size(move_lights(lights, t)))
+    return time
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()