Reverse String using Recursion

The recursive algorithm to reverse a string works by swapping the first and last characters until the middle of the string is reached. This process is performed through recursive calls, where in each call, characters at positions i and n-i-1 are swapped, and i is incremented. This continues until i reaches n/2, and the string is completely reversed.

Define a recursive function that takes a string as input.
If the string is empty or has only one character, return the string as it is the base case.
Otherwise, call the function recursively with the substring excluding the first character.
Append the first character to the result of the recursive call.

Below is the implementation of the above approach:

C++

// Recursive C++ program to reverse a string
#include <bits/stdc++.h>
using namespace std;
 
// Recursive function to reverse the string
void recursiveReverse(string &str, int i = 0)
{
    int n = str.length();
    if (i == n / 2)
        return;
  // Swap the i and n-i-1 character
    swap(str[i], str[n - i - 1]);
  // Call Recursive function after incrementing i.
    recursiveReverse(str, i + 1);
}
 
// Driver program
int main()
{
    string str = "w3wiki";
    recursiveReverse(str);
    cout << str;
    return 0;
}

Java

// Recursive Java program to reverse a string
import java.io.*;
class GFG 
{
 
  // Recursive function to reverse the string
static void recursiveReverse(char[] str, int i)
{
    int n = str.length;
   
    if (i == n / 2)
        return;
   
  // Swap the i and n-i-1 character
    swap(str,i,n - i - 1);
   
  // Call Recursive function after incrementing i.
    recursiveReverse(str, i + 1);
}
static void swap(char []arr, int i, int j)
{
    char temp= arr[i];
    arr[i]=arr[j];
    arr[j]=temp;
} 
 
// Driver program
public static void main(String[] args) 
{
    char[] str = "w3wiki".toCharArray();
    recursiveReverse(str,0);
    System.out.println(String.valueOf(str));
}
}
 
// This code is contributed by 29AjayKumar

Python3

# Recursive Python program to reverse a string
 
def recursiveReverse(str, i = 0):
    n = len(str)
 
    if i == n // 2:
        return
    # Swap the i and n-i-1 character
    str[i], str[n-i-1] = str[n-i-1], str[i]
     
    # Call Recursive function after incrementing i.
    recursiveReverse(str, i+1)
 
if __name__ == "__main__":
    str = "w3wiki"
 
    # converting string to list
    # because strings do not support
    # item assignment
    str = list(str)
    recursiveReverse(str)
 
    # converting list to string
    str = ''.join(str)
    print(str)
 
# This code is contributed by 
# sanjeev2552

C#

// Recursive C# program to reverse a string
using System;
 
public class GFG 
{
  
static void recursiveReverse(char[] str, int i)
{
    int n = str.Length;
    if (i == n / 2)
        return;
   
  // Swap the i and n-i-1 character
    swap(str,i,n - i - 1);
   
  // Call Recursive function after incrementing i.
    recursiveReverse(str, i + 1);
}
static char[] swap(char []arr, int i, int j)
{
    char temp= arr[i];
    arr[i]=arr[j];
    arr[j]=temp;
    return arr;
} 
  
// Driver program
public static void Main(String[] args) 
{
    char[] str = "w3wiki".ToCharArray();
    recursiveReverse(str,0);
    Console.WriteLine(String.Join("",str));
}
}
// This code is contributed by Princi Singh

Javascript

// Recursive JavaScript function to reverse a string
function recursiveReverse(str, i = 0) {
    const n = str.length;
    if (i >= Math.floor(n / 2))
        return str;
    // Swap the i and n-i-1 characters
    str = str.substring(0, i) + str[n - i - 1] + str.substring(i + 1, n - i - 1) + str[i] + str.substring(n - i);
    // Call Recursive function after incrementing i.
    return recursiveReverse(str, i + 1);
}
 
// Driver program
    let str = "w3wiki";
    str = recursiveReverse(str);
    console.log(str);

PHP

<?php
// A Simple PHP program
// to reverse a string
 
// Function to reverse a string
function reverseStr($str)
{
 
    // print the string
    // from last
    echo strrev($str);
}
 
// Driver Code
$str = "w3wiki";
 
reverseStr($str);
 
// This code is contributed
// by Srathore
?>

Output

skeegrofskeeg

Time Complexity: O(n) where n is length of string
Auxiliary Space: O(n)

String Reverse in C/C++/Java/Python/JavaScript

String reverse or reverse a string means changing the position of each character of the given string to its opposite position from end, i.e. if a character is at position 1 then its new position will be String.length, similarly if a character is at position 2 then its new position will be String.length – 1, and so on.

String Reverse in C/C++/Java/Python/JavaScript

Given a string, write a program to reverse the string.

Input: original_string[] = Geeks
Output: string_reversed[] = skeeG

Input: original_string[] = w3wiki
Output: string_reversed[] = skeeGroFskeeG

Table of Content

Reverse String using a Loop:
Reverse String using inbuilt method
Reverse String using Recursion:
Reverse String using two pointers:
String Reverse String using Stack:

Tags:

#Reverse #DSA #Strings #Reverse #Strings

Reverse String using inbuilt method

Reverse String using two pointers:

Reverse String using Recursion

C++

Java

Python3

C#

Javascript

PHP

String Reverse in C/C++/Java/Python/JavaScript

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