can cross river?

cross_river.rb

river = “************~~~”

river1 = “****~~~~”

river2 = “****************~~*~~~*”

# NOTES:
#
# acc. by 1
# stay the same speed
# dec. by 1
#
# first time speed 1
# can move 1, 2
# next time move 2
# can move 1, 2, 3

river = river.split('')

def can_cross?(river, pos=0, speed=0)

  eventually_cross_river?(river, 0)

end

def eventually_cross_river?(arr, speed)

  return speed if !arr || arr.length == 0

  return false if !arr[0]

  determine_next_speed(0..speed).each do |next_speed|
    possible_speeds = eventually_cross_river?(arr[next_speed...arr.length], next_speed)

    return [speed] + possible_speeds
  end

  return false

end

def determine_next_speed(speed)

  possible_speeds = []

  dec_speed = speed - 1

  possible_speeds << dec_speed if dec_speed > 0

  possible_speeds << speed

  possible_speeds << speed + 1

  return possible_speeds

end