Sorry for not adding the input/output. Will check for those

Python solutions are broken, in some cases it says that the solution should be longer than the input list!

  def diamond(m):
      if m % 2 == 1 and m > 0:
          n = (m - 1) / 2
          s = []
          for i in xrange(n, -1, -1):
              s += [i * ' ', '*' * (m - 2 * i), '\n']
          for i in xrange(1, n+1):
              s += [i * ' ', '*' * (m - 2 * i), '\n']
          return ''.join(s)
      else:
          return None

It returns False if you input "", which intuitively seems wrong because all count to zero.