flatten.rb

class Array
 
  ## Here i want to flatten an array
  ## by a given number of dimensions if an argument is passed
  def my_flatten(n = nil)
    n ? multiple_flatten(self, n) : recursive_flatten(self)
  end

  private

  ## flattening an array by one diemention
  ## Example:
  ## array = [1, [2, 3, [4, 5]]]
  ## single_flatten(array) #=> [1, 2, 3, [4, 5]]
  def single_flatten(array)
    array.each do |element|
      if element.class == Array
        element.each {|value| results << value}
      else
        results << element
      end
    end

    results
  end

  ## flattening an array N times
  ## Example:
  ## array = [1, [2, 3, [4, [5, 6]]]]
  ## multiple_flatten(my_array, 2) #=> [1, 2, 3, 4, [5, 6]]
  def multiple_flatten(array, n)
    count = 0
    arr   = array
    while count < n do
      arr = single_flatten(arr)
      count += 1
    end

    arr
  end

  ## flattening an array with recursion
  ## Eample:
  ## array = [1, [2, 3, [4, 5]]]
  ## recursive_flatten(my_array) #=> [1, 2, 3, 4, 5]
  def recursive_flatten(array, results = [])
    array.each do |element|
      if element.class == Array
        recursive_flatten(element, results)
      else
        results << element
      end
    end
    
    results
  end
end