docs: def sprinkler_reaches_cell(x, y, sx, sy, r):
      """
      Return whether a cell is within the radius of the sprinkler.
  
      x:  column index of cell
      y:  row index of cell
      sx:  column index of sprinkler
      sy:  row index of sprinkler
      r:  sprinkler radius
      """
      dx = sx - x
      dy = sy - y
      return math.sqrt(dx ** 2 + dy ** 2) <= r