class Solution:
    def reverseString(self, s: List[str]) -> None:
        """
        Do not return anything, modify s in-place instead.
        """
        front = 0
        n = len(s)
        rear = n - 1
        for i in range(n):
            if front < rear:
                temp = s[rear]
                s[rear] = s[front]
                s[front] = temp
                front += 1
                rear -= 1