344. Reverse String

https://leetcode.com/problems/reverse-string

Python

Loop

class Solution:
    def reverseString(self, s: List[str]) -> None:
        """
        Do not return anything, modify s in-place instead.
        """
        length = len(s)
        max_index = length - 1

        for i in range(0, length//2):
            s[i], s[max_index-i] = s[max_index-i], s[i]

Recursion

class Solution:
    def reverseString(self, s: List[str]) -> None:
        """
        Do not return anything, modify s in-place instead.
        """
        self._travel(s, 0, len(s)-1)

    def _travel(self, s, left, right):
        if left >= right:
            return

        s[left], s[right] = s[right], s[left]
        self._travel(s, left+1, right-1)

Stack

class Solution:
    def reverseString(self, s: List[str]) -> None:
        stack = []
        for char in s:
            stack.append(char)

        i = 0
        while stack:
            s[i] = stack.pop()
            i += 1