advent_17_part2.py

def simulate(dx, dy, x1, x2, y1, y2):
  x, y = (0, 0)
  initial_dx, initial_dy = dx, dy
  while True:
    x += dx
    y += dy
    dy -= 1
    if dx < 0:
      dx += 1
    elif dx > 0:
      dx -= 1
    if x >= x1 and x <= x2 and y >= y1 and y <= y2:
      return True
    if x < x1 or x > x2:
      if dx == 0:
        # If dx is 0 and not in range, we'll never hit the target.
        return False
    if x > x2 or y < y1:
      return False
  return False

def find_best_dy(dx, x1, x2, y1, y2):
  dy = 999
  have_found_hit = False
  count = 0
  while dy > -999:
    hit = simulate(dx, dy, x1, x2, y1, y2)
    if hit:
      have_found_hit = True
      count += 1
    dy -= 1
  return count


def find_trajectory(x1, x2, y1, y2):
  x1, x2 = sorted([x1, x2])
  y1, y2 = sorted([y1, y2])
  # Initial dx must be at most x2, otherwise it'll fall out of bounds.
  dx = x2
  best_solution = -999999
  best_dy = 0
  best_dx = 0
  count = 0
  while dx > 0:
    count += find_best_dy(dx, x1, x2, y1, y2)
    dx -= 1
  print(count)

find_trajectory(25, 67, -260, -200)