message: Add alternative solution for 'Find all duplicates in an array'
diff: @@ -33,3 +33,15 @@ class Solution(object):
  if i != nums[i]-1:
  result.append(nums[i])
  return result
  +
  +
  +from collections import Counter
  +
  +
  +class Solution2(object):
  + def findDuplicates(self, nums):
  + """
  + :type nums: List[int]
  + :rtype: List[int]
  + """
  + return [elem for elem, count in Counter(nums).items() if count == 2]
  