Leetcode 344. Reverse String

Problem

Write a function that reverses a string. The input string is given as an array of characters s.

You must do this by modifying the input array in-place with O(1) extra memory.

Algorithm

Just exchange the i th item with the len(s)-1-i th item.

Code

class Solution:
    def reverseString(self, s: List[str]) -> None:
        """
        Do not return anything, modify s in-place instead.
        """
        slen = len(s)
        for i in range(slen // 2):
            temp = s[i]
            s[i] = s[slen-1-i]
            s[slen-1-i] = temp