text: class Solution:
      def reverseString(self, s: List[str]) -> None:
          """
          Do not return anything, modify s in-place instead.
          """
          i = 0
          j = len(s)-1
          
          while i<j:
              s[i],s[j] = s[j],s[i]
              i+=1
              j-=1
  
  # Time: O(N)
  # Space:O(1)