BouncingBall.rb

=begin

A child plays with a ball on the nth floor of a big building the height of which
is known

(float parameter "h" in meters, h > 0) .

He lets out the ball. The ball rebounds for example to two-thirds

(float parameter "bounce", 0 < bounce < 1)

of its height.

His mother looks out of a window that is 1.5 meters from the ground

(float parameters window < h).

How many times will the mother see the ball either falling or bouncing in front
of the window

(return a positive integer unless conditions are not fulfilled in which case
return -1) ?

Note

You will admit that the ball can only be seen if the height of the rebouncing
ball is stricty greater than the window parameter.

Example:

h = 3, bounce = 0.66, window = 1.5, result is 3

h = 3, bounce = 1, window = 1.5, result is -1

=end

# My Solution
def bouncingBall(h, bounce, window, times=0)
    return -1 if bounce >= 1 || bounce <= 0
    if window > h
      if times == 0
        return -1
      else
        return times
      end
    end
    times += 1 if h > window
    h = h.to_f * bounce
    times += 1 if h > window
    bouncingBall(h, bounce, window, times)
end

# Better Solution
def bouncingBall(h, bounce, window)
  bounce > 0 && bounce < 1 && window < h ? 1 + 2*Math.log(window.to_f/h,bounce).floor : -1
end

# Another Solution
def bouncingBall(height, bounce, window)
  return -1 unless (0...1).cover?(bounce)
  bounce_heights = [height]
  while bounce_heights.last > window
    bounce_heights << bounce_heights.last * bounce
  end
  (bounce_heights.size-1) * 2 - 1
end