class Solution:
  def reverseVowels(self, s: str) -> str:
    vowels = set('aeiouAEIOU')
    s_list = list(s)
    left, right = 0, len(s) -1
    while left < right:
      if s_list[left] not in vowels:
        left += 1
      elif s_list[right] not in vowels:
        right -= 1
      else:
        s_list[left], s_list[right] = s_list[right], s_list[left]
        left += 1
        right -= 1
    return ''.join(s_list)