message: Minor readability improvement
diff: @@ -20,7 +20,7 @@ class Solution:
  def permuteRecu(self, result, used, cur, num):
  if len(cur) == len(num):
  - result.append(cur + [])
  + result.append(cur[:])
  return
  for i in xrange(len(num)):
  if not used[i]:
  