Reverse String in Python

Suppose we have an array of characters. We have to reverse the string without using any additional space. So if the string is like [‘H’, ‘E’, ‘L’, ‘L’, ‘O’], the output will be [‘O’, ‘L’, ‘L’, ‘E’, ‘H’]

To solve this, we will follow these steps −

• Take two pointers to start = 0 and end = length of the string – 1
• swap first and last characters
• increase start by 1 and decrease-end by 1

Example

Let us see the following implementation to get a better understanding −

 Live Demo

class Solution(object):
   def reverseString(self, s):
      """
      :type s: List[str]
      :rtype: None Do not return anything, modify s in-place instead.
      """
      start = 0
      end = len(s)-1
      while start<end:
         s[start],s[end] = s[end],s[start]
         start+=1
         end-=1string_1 = ["H","E","L","L","O"]
ob1 = Solution()
ob1.reverseString(string_1)
print(string_1)

Input

String = ["H","E","L","L","O"]

Output

["O","L","L","E","H"]