Reverse an array in-place — C# Programming

Problem

Reverse { 1, 2, 3, 4, 5 } in-place and print elements.

Hints

Use two indices: left at 0, right at Length-1.

Your practice code

Ready — edit the code above and click Run.

Solution

using System;

class Program
{
    static void Main()
    {
        int[] arr = { 1, 2, 3, 4, 5 };
        int left = 0, right = arr.Length - 1;
        while (left < right)
        {
            (arr[left], arr[right]) = (arr[right], arr[left]);
            left++; right--;
        }
        Console.WriteLine(string.Join(", ", arr));
    }
}

Try solving on your own first, then reveal the official answer.

Explanation

Two-pointer swap from both ends—O(n/2) swaps. Tuple swap syntax is clean in modern C#.