Reverse an Array in C++

This section will discuss the different ways to reverse an array in the C++ programming language. The reverse of an array means to change the order of the given array's elements. This technique reverses the last element of the array into the first one, and the first element becomes the last. However, the process continues until all characters or elements of the array are completely reversed.

For example, the array contains elements like 'H', 'E', 'L', 'L', 'O', and when we reverse all the elements of an array, it returns the inverted array as 'O', 'L', 'L', 'E', 'H'. So, this way, all the characters in the array are reversed.

Different ways to reverse an array

Following are the various ways to get the reverse array in the C++ programming language.

Reverse an array using for loop
Reverse an array using the reverse() function
Reverse an array using the user-defined function
Reverse an array using the pointers
Reverse an array using the Recursion function

Program to reverse an array using the for loop

Let's create a program to reverse the elements of the array using for loop in C++.

Program1.cpp

#include <iostream>
using namespace std;

int main ()
{
	int arr[50], num, temp, i, j;
	cout << " Please, enter the total no. you want to enter: ";
	cin >> num;
	
	// use for loop to enter the numbers 
	for (i = 0; i < num; i++)
	{
		cout << " Enter the element " << i+1 << ": ";
		cin >> arr[i];
	}
	
	
	for ( i = 0, j = num - 1; i < num/2; i++, j--)
	{	
		temp = arr[i];
		arr[i] = arr[j];
		arr[j] = temp;
	}
	cout << "\n Reverse all elements of the array: " << endl;
	// use for loop to print the reverse array
	for ( i = 0; i < num; i++)
	{
		cout << arr[i] << " ";
	}
	return 0;
}

Output

Please, enter the total no. you want to enter: 6
 Enter the element 1: 78
 Enter the element 2: 12
 Enter the element 3: 54
 Enter the element 4: 24
 Enter the element 5: 7
 Enter the element 6: 90

 Reverse all elements of the array:
90 7 24 54 12 78

Program to reverse an array using the reverse() function

Let's consider an example to print the reverse of an array using the reverse () function in C++.

Program2.cpp

#include <iostream>
#include <algorithm>
using namespace std;

// declare disp() function 
void disp(int arr1[], int num)
{
	int i;
	// use for loop to iterate the characters
	for ( i = 0; i < num; i++)
	{
		cout << arr1[i] << " ";
	}
}

// define reverse() function to reverse the array elements
void reverse(int arr1[], int num)
{
	reverse(arr1, arr1 + num); 
}

int main ()
{
	// declare and initialize an array
	int arr1[] = {34, 78, 21, 90, 5, 2};
	int num = sizeof(arr1)/sizeof(arr1[0]);
	
	// call reverse function and pass parameters
	reverse(arr1, num);
	disp(arr1, num); /* call disp() function to print the revrse array. */
	
	return 0; 
}

Output

2 5 90 21 78 34

Program to reverse an array using the user-defined function

Let's consider an example to display the reverse of array elements using the user-defined in C++.

Program3.cpp

#include <iostream>
using namespace std;

void ArrRev ( int [], int);
int main ()
{
	int arr[50], num, i, j, temp;
	cout << " Number of elements to be entered: " << endl;
	cin >> num;
		
	cout << " Enter the array elements: " << endl;
	
	// use for loop to enter the elements
	for ( i = 0; i < num; i++)
	{
		cin >> arr[i];
	}
	cout << " Elements are: \n";
	// display entered elements in array
	for ( i = 0; i < num; i++)
	{
		cout << arr[i] << " ";
	}
	ArrRev (arr, num); // call function
	
	cout << " \n The reverse of the given array is: \n";
	// use for loop to print the reverse array elements
	for ( i = 0; i < num ; i++)
	{
		cout << arr[i] << " ";
	}
	cout << endl;
	return 0;
}

void ArrRev ( int ar[], int a2)
{
	int i, j, temp;
	j = a2 - 1;
	for ( i = 0; i < j; i++, j--)
	{
		temp = ar[i];
		ar[i] = ar[j];
		ar[j] = temp;
	}
}

Output

Number of elements to be entered:
7
 Enter the array elements:
45
32
89
21
78
34
65
 Elements are:
45 32 89 21 78 34 65
 The reverse of the given array is:
65 34 78 21 89 32 45

Program to reverse an array using the pointer

Let's consider an example to demonstrate the reversing of the array elements using the pointers in C++.

Program4.cpp

#include <iostream>
using namespace std;
int main ()
{
	// declare the size of array
	int arr[50], arr2[50];
	int *ptr, i, num;
	cout <<" No. of array elements to be entered: "<< endl;
	cin >> num;	
	
	cout <<" Enter the elements: ";
	// use for loop to insert the array elements
	for (i = 0; i < num; i++)
	{
		cin >> arr[i];
	}
	ptr = &arr[0];
	cout <<" Entered elements of the array are: \n" <<endl;
	for (i = 0; i < num; i++)
	{
		cout << "\t" << *ptr;
		ptr++;
	}
	ptr--; // decrement ptr
	for ( i = 0; i < num; i++)
	{
		arr2[i] = *ptr;
		ptr--;
	}
	ptr = &arr2[0];
	for ( i = 0; i < num; i++)
	{
		arr[i] = *ptr;
		ptr++; // increment ptr
	}
	ptr = &arr[0]; // ptr hold the base address of arr[0]
	cout <<" \n The reversed array elements are: \n " << endl;
	
	// print the array elements using ptr
	for ( i = 0; i < num; i++)
	{
		cout <<" \t " << *ptr <<endl;
		ptr++;
	}
	return 0;
}

Output

No. of array elements to be entered:
6
 Enter the elements: 45
32
89
63
4
6
 Entered elements of the array are:

        45      32      89      63      4       6
 The reversed array elements are:

         6
         4
         63
         89
         32
         45

Reverse an array using the Recursion function

Let's create a program to reverse the array elements using the recursion function in C++.

Program5.cpp

#include <iostream>
using namespace std;

// initialize array
int arr[] = { 20, 34, 5, 8, 1, 78};

// size of the array
int size = sizeof( arr) / sizeof (arr[0]);

void reverseArr ( int arr[] , int num)
{
	// check the size of array
	if ( num == size)
		return;
	
	// extract array elements
	int elem = arr [ num];
	
	// recursively calls the next element of the array
	reverseArr ( arr, num + 1);
	// assigning elements
	arr [ size - num - 1] = elem;
}

int main ()
{
	int i;
	// call recursive function (start from first elements
	cout << " Original elements of the arrays " << endl;
	for ( int i = 0; i < size; i++)
	{
		cout << arr[i] << " ";
	}
	
	reverseArr (arr, 0);
	cout << " \n Reverse elements of the array are: " << endl;
	// display the array elements
	for ( int i = 0; i < size; i++)
	{
		cout << arr[i] << " ";
	}
	return 0;
}

Output

Original elements of the arrays
20 34 5 8 1 78
 Reverse elements of the array are:
78 1 8 5 34 20

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Reverse an Array in C++

Different ways to reverse an array

Program to reverse an array using the for loop

Program to reverse an array using the reverse() function

Program to reverse an array using the user-defined function

Program to reverse an array using the pointer

Reverse an array using the Recursion function

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