PrestandaDemo/Sortering/Program.cs

using System.Diagnostics;

class Program {
    static void Main() {
        while (true) {
            Console.WriteLine();
            Console.WriteLine("=== Prestanda-Sorteringsmeny ===");
            Console.WriteLine("1: Bubblesort (O(n^2))");
            Console.WriteLine("2: Inbyggd snabb sortering (Array.Sort)");
            Console.WriteLine("0: Avsluta");
            Console.Write("Ditt val: ");

            var choice = Console.ReadLine();
            if (choice == "0") {
                Console.WriteLine("Avslutar...");
                break;
            }

            int n = ReadPositiveInt("Hur många tal vill du sortera? ");

            int[] data = CreateRandomArray(n, maxValue: n * 10);
            Console.WriteLine();
            Console.WriteLine($"Osorterat: {Preview(data)}");

            var copy = (int[])data.Clone();

            var sw = Stopwatch.StartNew();
            switch (choice) {
                case "1":
                    BubbleSort(copy);
                    break;
                case "2":
                    FastSort(copy);
                    break;
                default:
                    Console.WriteLine("Ogiltigt val. Försök igen.");
                    continue;
            }

            sw.Stop();

            Console.WriteLine($"Sorterad:  {Preview(copy)}");
            Console.WriteLine($"Tid: {sw.ElapsedMilliseconds} ms för n = {n}");
        }
    }

    static int ReadPositiveInt(string prompt) {
        while (true) {
            Console.Write(prompt);
            if (int.TryParse(Console.ReadLine(), out int n) && n > 0)
                return n;
            Console.WriteLine("Ange ett heltal större än 0.");
        }
    }

    static int[] CreateRandomArray(int n, int maxValue) {
        var rnd = new Random();
        var arr = new int[n];
        for (int i = 0; i < n; i++)
            arr[i] = rnd.Next(maxValue + 1);
        return arr;
    }

    static string Preview(int[] arr, int head = 10, int tail = 10) {
        if (arr.Length <= head + tail)
            return string.Join(", ", arr);

        var headPart = string.Join(", ", arr[..head]);
        var tailPart = string.Join(", ", arr[^tail..]);
        return $"{headPart}, … , {tailPart}";
    }

    public static void BubbleSort(int[] arr) {
        int n = arr.Length;
        bool swapped;
        for (int pass = 0; pass < n - 1; pass++) {
            swapped = false;
            for (int i = 0; i < n - 1 - pass; i++) {
                if (arr[i] > arr[i + 1]) {
                    int tmp = arr[i];
                    arr[i] = arr[i + 1];
                    arr[i + 1] = tmp;
                    swapped = true;
                }
            }

            if (!swapped) break;
        }
    }

    public static void FastSort(int[] arr) {
        Array.Sort(arr);
    }
}