message: add another solution
  using most_common(1) instead of sorting counter object reduces
  time complexity from O(nlogn) to O(n)
diff: @@ -30,3 +30,9 @@ class Solution(object):
  """
  return sorted(collections.Counter(nums).items(), key=lambda a: a[1], reverse=True)[0][0]
  + def majorityElement3(self, nums):
  + """
  + :type nums: List[int]
  + :rtype: int
  + """
  + return collections.Counter(nums).most_common(1)[0][0]
  