How to Reverse an Array in C# with Examples

In this article, we’ll learn how to reverse an array in C# with multiple examples and code explanations.

Introduction

Reversing an array might seem like a simple task, but it’s a fundamental operation in programming. Mastering array reversal is essential if you’re dealing with data structures and algorithms or want to impress your fellow developers at the next code review.

The Problem

Given an array, how do we reverse its elements? Imagine you have an array like this:

int[] originalArray = { 1, 2, 3, 4, 5 };

Your goal is to transform it into:

int[] reversedArray = { 5, 4, 3, 2, 1 };

Method 1: Using the Array.Reverse() Method

In this example, we use the built-in Array.Reverse() method to reverse the elements of the array.

// Code Example 1: Using Array.Reverse() Method
using System;

class Program
{
    static void Main()
    {
        // Original array
        int[] originalArray = { 1, 2, 3, 4, 5 };

        // Display original array
        Console.WriteLine("Original Array: " + string.Join(", ", originalArray));

        // Reverse the array using Array.Reverse() method
        Array.Reverse(originalArray);

        // Display reversed array
        Console.WriteLine("Reversed Array: " + string.Join(", ", originalArray));
    }
}

Output:

Original Array: 1, 2, 3, 4, 5
Reversed Array: 5, 4, 3, 2, 1

Method 2: Reverse an Array in C# using Temporary Array

In this example, we manually reverse the array by creating a temporary array and iterating through the original array in reverse order.

// Code Example 2: Manual Reversal with a Temporary Array
using System;

class Program
{
    static void Main()
    {
        // Original array
        int[] originalArray = { 1, 2, 3, 4, 5 };

        // Display original array
        Console.WriteLine("Original Array: " + string.Join(", ", originalArray));

        // Create a temporary array to store reversed elements
        int[] reversedArray = new int[originalArray.Length];

        // Perform manual reversal
        for (int i = 0, j = originalArray.Length - 1; i < originalArray.Length; i++, j--)
        {
            reversedArray[i] = originalArray[j];
        }

        // Display reversed array
        Console.WriteLine("Reversed Array: " + string.Join(", ", reversedArray));
    }
}

Output:

Original Array: 1, 2, 3, 4, 5
Reversed Array: 5, 4, 3, 2, 1

Method 3: Using LINQ to Reverse an Array in C#

This example showcases how to use LINQ (Language Integrated Query) to reverse an array effortlessly. In the LINQ, we can use the Reverse() method, combined with ToArray(), to reverse an array.

// Code Example 3: Using LINQ to Reverse an Array
using System;
using System.Linq;

class Program
{
    static void Main()
    {
        // Original array
        int[] originalArray = { 1, 2, 3, 4, 5 };

        // Display original array
        Console.WriteLine("Original Array: " + string.Join(", ", originalArray));

        // Use LINQ to reverse the array
        int[] reversedArray = originalArray.Reverse().ToArray();

        // Display reversed array
        Console.WriteLine("Reversed Array: " + string.Join(", ", reversedArray));
    }
}

Output:

Original Array: 1, 2, 3, 4, 5
Reversed Array: 5, 4, 3, 2, 1

Method 4: The Swapping Technique To Reverse an Array in C#

Our approach involves swapping elements within the array. Let’s break it down:

The Swapping Technique

• Swapping Elements: We’ll swap pairs of elements to reverse an array. For example, if we have elements 3 and 4, we’ll replace 3 with 4 and vice versa. Here’s how it works:

• Create a temporary variable to store the value at the first index (let’s call it temp).
• Replace the value at the second index with the value at the first index.
• Finally, replace the value at the first index with temp.

• Iterative Swapping: We’ll apply this swapping technique iteratively. Starting from both ends of the array, we’ll move toward the center until the start index is less than the end index.

The Algorithm

Here’s the step-by-step algorithm to reverse an array:

1. Initialize two variables: startIndex (set to 0) and endIndex (set to n-1, where n is the array length).
2. Swap the values at startIndex and endIndex.
3. Increment startIndex by 1 and decrement endIndex by 1.
4. Repeat steps 2 and 3 until the startIndex is less than the endIndex.
5. Great! You’ve reversed the array.

Let’s Code!

Enough theory; let’s dive into some C# code. Below is a sample program that reverses an array using the swapping technique:

using System;

namespace ReverseAnArrayExample
{
    public class Program
    {
        static void Main(string[] args)
        {
            int[] arr = { 1, 2, 3, 4, 5 };

            Console.Write("Original Array: ");
            for (int i = 0; i < arr.Length; i++)
            {
                Console.Write(arr[i] + " ");
            }

            ReverseArrayElements(arr, 0, arr.Length - 1);

            Console.Write("\nReversed Array: ");
            for (int i = 0; i < arr.Length; i++)
            {
                Console.Write(arr[i] + " ");
            }

            Console.ReadKey();
        }

        public static void ReverseArrayElements(int[] arr, int startIndex, int endIndex)
        {
            while (startIndex < endIndex)
            {
                int temp = arr[startIndex];
                arr[startIndex] = arr[endIndex];
                arr[endIndex] = temp;
                startIndex++;
                endIndex--;
            }
        }
    }
}

Output:

Original Array: 1 2 3 4 5 
Reversed Array: 5 4 3 2 1

Conclusion:

Reversing an array in C# is a common operation, and understanding different methods for achieving this task is crucial for every developer, whether you prefer simply the “Array.Reverse()” method, the manual approach with a temporary array, or the use of LINQ to reverse an array.

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Shekh Ali

Meet Sheikh Ali, a skilled Software engineer and passionate a blogger. He enjoys sharing his expertise in C#, Java, SQL, Design Patterns, and other related topics through his writing. When he's not coding, Sheikh Ali can often indulge in his passions for reading books and fitness training.

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