old_contents: """Codewars: Draw stairs
  8 kyu
  
  URL: https://www.codewars.com/kata/draw-stairs/
  
  Given a number n, draw stairs using the letter "I", n tall and n wide,
  with the tallest in the top left.
  
  For example n = 3 result in "I\n I\n I", or printed:
  I
   I
    I
  
  Another example, a 7-step stairs should be drawn like this:
  I
   I
    I
     I
      I
       I
        I
  """
  
  def draw_stairs(n):
      stairs = []
      
      for i in range(n):
          # Append (i - 1) spaces.
          for  _ in range(i):
              stairs.append(' ')
          
          # Append stair I.
          stairs.append('I')
          
          # Append change line if not the last line.
          if i != n - 1:
              stairs.append('\n')
      
      return ''.join(stairs)
  
  
  def main():
      # Output: "I\n I\n I" 
      n = 3
      print draw_stairs(n)
  
      # Output: "I\n I\n I\n   I\n    I\n     I\n      I\n       I" 
      n = 7
      print draw_stairs(n)
  
  
  if __name__ == '__main__':
      main()
  
new_contents: """Codewars: Draw stairs
  8 kyu
  
  URL: https://www.codewars.com/kata/draw-stairs/
  
  Given a number n, draw stairs using the letter "I", n tall and n wide,
  with the tallest in the top left.
  
  For example n = 3 result in "I\n I\n I", or printed:
  I
   I
    I
  
  Another example, a 7-step stairs should be drawn like this:
  I
   I
    I
     I
      I
       I
        I
  """
  
  def draw_stairs(n):
      """
      Time complexity: O(n^2).
      Space complexity: O(n).
      """
      stairs = []
      
      for i in range(n):
          # Append (i - 1) spaces.
          stairs.append(' ' * i)
          
          # Append stair I.
          stairs.append('I')
          
          # Append change line if not the last line.
          if i != n - 1:
              stairs.append('\n')
      
      return ''.join(stairs)
  
  
  def main():
      # Output: "I\n I\n I" 
      n = 3
      print draw_stairs(n)
  
      # Output: "I\n I\n I\n   I\n    I\n     I\n      I\n       I" 
      n = 7
      print draw_stairs(n)
  
  
  if __name__ == '__main__':
      main()
  
subject: Simplify adding spaces and add time/space complexity