How to reverse an Array or String ?

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We have taken some example to reverse an Array or String.

Ex:

Input  : arr[] = {1, 2, 3}
Output : arr[] = {3, 2, 1}

Input :  arr[] = {4, 5, 1, 2}
Output : arr[] = {2, 1, 5, 4}
1. Initialize start and end indexes as start = 0, end = n-1 
2. In a loop, swap arr[start] with arr[end] and change start and end as follows : 
3.start = start +1, end = end – 1

Start writing code on your compiler :

C++ Solution:

// Iterative C# program to reverse an
// array
using System;
 
class Program {
 
    /* Function to reverse arr[] from
    start to end*/
    static void rvereseArray(int []arr,
                    int start, int end)
    {
        int temp;
         
        while (start < end)
        {
            temp = arr[start];
            arr[start] = arr[end];
            arr[end] = temp;
            start++;
            end--;
        }
    }    
     
    /* Utility that prints out an
    array on a line */
    static void printArray(int []arr,
                            int size)
    {
        for (int i = 0; i < size; i++)
            Console.Write(arr[i] + " ");
         
        Console.WriteLine();
    }
     
    // Driver function
    public static void Main()
    {
        int []arr = {1, 2, 3, 4, 5, 6};
        printArray(arr, 6);
        rvereseArray(arr, 0, 5);
        Console.Write("Reversed array is \n");
        printArray(arr, 6);
    }
}

C Solution:

// Iterative C program to reverse an array
#include<stdio.h>
 
/* Function to reverse arr[] from start to end*/
void rvereseArray(int arr[], int start, int end)
{
    int temp;
    while (start < end)
    {
        temp = arr[start];  
        arr[start] = arr[end];
        arr[end] = temp;
        start++;
        end--;
    }  
}    
 
/* Utility that prints out an array on a line */
void printArray(int arr[], int size)
{
  int i;
  for (i=0; i < size; i++)
    printf("%d ", arr[i]);
 
  printf("\n");
}
 
/* Driver function to test above functions */
int main()
{
    int arr[] = {1, 2, 3, 4, 5, 6};
    int n = sizeof(arr) / sizeof(arr[0]);
    printArray(arr, n);
    rvereseArray(arr, 0, n-1);
    printf("Reversed array is \n");
    printArray(arr, n);   
    return 0;
}

Java Solution:

// Iterative java program to reverse an
// array
public class Program {
     
   /* Function to reverse arr[] from
    start to end*/
    static void rvereseArray(int arr[],
                    int start, int end)
    {
        int temp;
          
        while (start < end)
        {
            temp = arr[start];
            arr[start] = arr[end];
            arr[end] = temp;
            start++;
            end--;
        }
    }    
      
    /* Utility that prints out an
    array on a line */
    static void printArray(int arr[],
                            int size)
    {
        for (int i = 0; i < size; i++)
             System.out.print(arr[i] + " ");
          
         System.out.println();
    }
 
    // Driver code
    public static void main(String args[]) {
         
        int arr[] = {1, 2, 3, 4, 5, 6};
        printArray(arr, 6);
        rvereseArray(arr, 0, 5);
        System.out.print("Reversed array is \n");
        printArray(arr, 6);
        
    }
}
 

Python Solution:

# Iterative python program to reverse an array
 
# Function to reverse A[] from start to end
def reverseList(A, start, end):
    while start < end:
        A[start], A[end] = A[end], A[start]
        start += 1
        end -= 1
 
# Driver function to test above function
A = [1, 2, 3, 4, 5, 6]
print(A)
reverseList(A, 0, 5)
print("Reversed list is")
print(A)

C# Solution:

// Iterative C# program to reverse an
// array
using System;
 
class Program {
 
    /* Function to reverse arr[] from
    start to end*/
    static void rvereseArray(int []arr,
                    int start, int end)
    {
        int temp;
         
        while (start < end)
        {
            temp = arr[start];
            arr[start] = arr[end];
            arr[end] = temp;
            start++;
            end--;
        }
    }    
     
    /* Utility that prints out an
    array on a line */
    static void printArray(int []arr,
                            int size)
    {
        for (int i = 0; i < size; i++)
            Console.Write(arr[i] + " ");
         
        Console.WriteLine();
    }
     
    // Driver function
    public static void Main()
    {
        int []arr = {1, 2, 3, 4, 5, 6};
        printArray(arr, 6);
        rvereseArray(arr, 0, 5);
        Console.Write("Reversed array is \n");
        printArray(arr, 6);
    }
}
 

PHP Solution:

<?php
// Iterative PHP program
// to reverse an array
 
/* Function to reverse
$arr from start to end*/
function rvereseArray(&$arr, $start,
                       $end)
{
    while ($start < $end)
    {
        $temp = $arr[$start];
        $arr[$start] = $arr[$end];
        $arr[$end] = $temp;
        $start++;
        $end--;
    }
}    
 
/* Utility function to
   print an array */
function printArray(&$arr, $size)
{
for ($i = 0; $i < $size; $i++)
echo $arr[$i] . " ";
 
echo "\n";
}
 
// Driver code
$arr = array(1, 2, 3, 4, 5, 6);
 
// To print original array
printArray($arr, 6);
 
// Function calling
rvereseArray($arr, 0, 5);
 
echo "Reversed array is" ."\n";
 
// To print the Reversed array
printArray($arr, 6);
 

JavaScript Solution:

// Iterative Javascript program to reverse an array
 
/* Function to reverse arr[] from start to end*/
function rvereseArray(arr,start,end)
{
    while (start < end)
    {  
        var temp = arr[start];
        arr[start] = arr[end];
        arr[end] = temp;
        start++;
        end--;
    }
}   
  
/* Utility function to print an array */
function printArray(arr,size)
{
   for (var i = 0; i < size; i++){
   console.log(arr[i]);
   }
}
  
/* Driver function to test above functions */
    var arr= [1, 2, 3, 4, 5, 6];
    var n = 6;
    // To print original array
    printArray(arr, n);
      
    // Function calling
    rvereseArray(arr, 0, n-1);
      
    console.log("Reversed array is");
      
   

Output :

1 2 3 4 5 6
Reversed array is:
6 5 4 3 2 1

Time Complexity : O(n)
Recursive Way :

1. Initialize start and end indexes as start = 0, end = n-1
2. Swap arr[start] with arr[end]
3. Recursively call reverse for rest of the array.

Below is the implementation of the above approach :

// Recursive C++ program to reverse an array
#include <bits/stdc++.h>
using namespace std;
 
/* Function to reverse arr[] from start to end*/
void rvereseArray(int arr[], int start, int end)
{
    if (start >= end)
    return;
     
    int temp = arr[start];
    arr[start] = arr[end];
    arr[end] = temp;
     
    // Recursive Function calling
    rvereseArray(arr, start + 1, end - 1);
}    
 
 
/* Utility function to print an array */
void printArray(int arr[], int size)
{
   for (int i = 0; i < size; i++)
   cout << arr[i] << " ";
 
   cout << endl;
}
 
/* Driver function to test above functions */
int main()
{
    int arr[] = {1, 2, 3, 4, 5, 6};
     
    // To print original array
    printArray(arr, 6);
     
    // Function calling
    rvereseArray(arr, 0, 5);
     
    cout << "Reversed array is" << endl;
     
    // To print the Reversed array
    printArray(arr, 6);
     
    return 0;
}
// Recursive C program to reverse an array
#include <stdio.h>
 
/* Function to reverse arr[] from start to end*/
void rvereseArray(int arr[], int start, int end)
{
   int temp;
   if (start >= end)
     return;
   temp = arr[start];  
   arr[start] = arr[end];
   arr[end] = temp;
   rvereseArray(arr, start+1, end-1);  
}    
 
/* Utility that prints out an array on a line */
void printArray(int arr[], int size)
{
  int i;
  for (i=0; i < size; i++)
    printf("%d ", arr[i]);
 
  printf("\n");
}
 
/* Driver function to test above functions */
int main()
{
    int arr[] = {1, 2, 3, 4, 5, 6};
    printArray(arr, 6);
    rvereseArray(arr, 0, 5);
    printf("Reversed array is \n");
    printArray(arr, 6);   
    return 0;
}
// Recursive Java Program to reverse an array
import java.io.*;
 
class ReverseArray {
 
    /* Function to reverse arr[] from start to end*/
    static void rvereseArray(int arr[], int start, int end)
    {
        int temp;
        if (start >= end)
            return;
        temp = arr[start];
        arr[start] = arr[end];
        arr[end] = temp;
        rvereseArray(arr, start+1, end-1);
    }
 
    /* Utility that prints out an array on a line */
    static void printArray(int arr[], int size)
    {
        for (int i=0; i < size; i++)
            System.out.print(arr[i] + " ");
        System.out.println("");
    }
 
    /*Driver function to check for above functions*/
    public static void main (String[] args) {
        int arr[] = {1, 2, 3, 4, 5, 6};
        printArray(arr, 6);
        rvereseArray(arr, 0, 5);
        System.out.println("Reversed array is ");
        printArray(arr, 6);
    }
}
# Recursive python program to reverse an array
 
# Function to reverse A[] from start to end
def reverseList(A, start, end):
    if start >= end:
        return
    A[start], A[end] = A[end], A[start]
    reverseList(A, start+1, end-1)
 
# Driver function to test above function
A = [1, 2, 3, 4, 5, 6]
print(A)
reverseList(A, 0, 5)
print("Reversed list is")
print(A)
<?php
// Iterative PHP program
// to reverse an array
 
/* Function to reverse
$arr from start to end*/
function rvereseArray(&$arr,
                       $start, $end)
{
    if ($start >= $end)
    return;
     
    $temp = $arr[$start];
    $arr[$start] = $arr[$end];
    $arr[$end] = $temp;
 
    //Recursive Function calling
    rvereseArray($arr, $start + 1,
                       $end - 1);
}    
 
/* Utility function
to print an array */
function printArray(&$arr, $size)
{
for ($i = 0; $i < $size; $i++)
echo $arr[$i] . " ";
 
echo "\n";
}
 
// Driver code
$arr = array(1, 2, 3, 4, 5, 6);
 
// To print original array
printArray($arr, 6);
 
// Function calling
rvereseArray($arr, 0, 5);
 
echo "Reversed array is" ."\n";
 
// To print the Reversed array
printArray($arr, 6);
 
// Recursive Javascript program to reverse an array
 
/* Function to reverse arr[] from start to end*/
function rvereseArray(arr,start,end)
{
    var temp = arr[start];
    arr[start] = arr[end];
    arr[end] = temp;
     
// Recursive Function calling
    if (start+1<end-1){
    rvereseArray(arr, start + 1, end - 1);
    }
}   
/* Utility function to print an array */
function printArray(arr,size)
{
for (var i = 0; i < size; i++){
console.log(arr[i]);
  }
}
 
/* Driver function to test above functions */
 
    var arr= [1, 2, 3, 4, 5, 6];
     
    // To print original array
    printArray(arr, 6);
     
    // Function calling
    rvereseArray(arr, 0, 5);
     
    console.log("Reversed array is");
     
    // To print the Reversed array
    printArray(arr, 6);

Output :

1 2 3 4 5 6
Reversed array is
6 5 4 3 2 1

Please suggest me if any other best solution you have.

Thanks

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