#!/usr/bin/env python import sys from typing import Iterator, List, NamedTuple class Point(NamedTuple): x: int y: int class Probe(NamedTuple): position: Point velocity: Point class Area(NamedTuple): min: Point max: Point def solve(input: List[str]) -> int: def parse(line: str) -> Area: x_range = line.split("x=")[1].split(",")[0] y_range = line.split("y=")[1] min_x, max_x = map(int, x_range.split("..")) min_y, max_y = map(int, y_range.split("..")) # Sanity check assert min_x <= max_x assert min_y <= max_y return Area(Point(min_x, min_y), Point(max_x, max_y)) def trajectory(p: Probe) -> Iterator[Probe]: def step(p: Probe) -> Probe: def drag(x: int) -> int: if x < 0: return x + 1 if x > 0: return x - 1 return 0 def gravity(y: int) -> int: return y - 1 pos, vel = p new_pos = Point(pos.x + vel.x, pos.y + vel.y) new_vel = Point(drag(vel.x), gravity(vel.y)) return Probe(new_pos, new_vel) while True: yield (p := step(p)) def hits_target(probe: Probe, area: Area) -> bool: # Too lazy to find an actual good condition on this loop, early break is enough for p in trajectory(probe): x, y = p.position # Early exit when we cannot possibly get to the area if y < area.min.y and p.velocity.y <= 0: break if x < area.min.x and p.velocity.x <= 0: break if x > area.max.x and p.velocity.x >= 0: break # Keep going if we're not in bounds if x < area.min.x or x > area.max.x: continue if y < area.min.y or y > area.max.y: continue # We are in the area return True return False def find_velocities(area: Area) -> Iterator[Point]: position = Point(0, 0) assert area.min.y < 0 # Sanity check, due to lower bound in loop # Can't overshoot after a single step for vx in range(0, area.max.x + 1): # Can't overshoot after a single step, symmetric velocity when coming down for vy in range(area.min.y, abs(area.min.y) + 1): velocity = Point(vx, vy) if hits_target(Probe(position, velocity), area): yield velocity target_area = parse(input[0]) velocities = set(find_velocities(target_area)) return len(velocities) def main() -> None: input = [line.strip() for line in sys.stdin.readlines()] print(solve(input)) if __name__ == "__main__": main()