---
tags: data_structure_python
---

# Reverse String <img src="https://img.shields.io/badge/-easy-brightgreen">

Write a function that reverses a string. The input string is given as an array of characters `char[]`.

Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

You may assume all the characters consist of printable ascii characters.

# Solution

class Solution:
    def reverseString(self, s: List[str]) -> None:
        """
        Do not return anything, modify s in-place instead.
        """
        # Time complexity: O(n).
        # Space complexity: O(n).
        self.__reverseString(s, 0, len(s)-1)
        
    def __reverseString(self, s, beg, end):
        if beg < end:
            s[beg], s[end] = s[end], s[beg]
            self.__reverseString(s, beg+1, end-1)