using System.Diagnostics;

class Program {
    static void Main() {
        while (true) {
            Console.WriteLine();
            Console.WriteLine("=== Prestanda-LINQ/Loop-meny ===");
            Console.WriteLine("1: Summa med LINQ");
            Console.WriteLine("2: Summa med loop");
            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 generera? ");

            var data = CreateRandomList(n, maxValue: n);

            var sw = Stopwatch.StartNew();
            long result = 0;

            switch (choice) {
                case "1":
                    result = SumWithLinq(data);
                    break;
                case "2":
                    result = SumWithLoop(data);
                    break;
                default:
                    Console.WriteLine("Ogiltigt val. Försök igen.");
                    continue;
            }

            sw.Stop();

            Console.WriteLine($"Resultat: {result}");
            Console.WriteLine($"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 List<long> CreateRandomList(int n, int maxValue) {
        var rnd = new Random();
        var list = new List<long>(n);
        for (int i = 0; i < n; i++)
            list.Add(rnd.Next(-maxValue, maxValue));
        return list;
    }

    static long SumWithLinq(IEnumerable<long> numbers) {
        return numbers.Where(n => n > 0).Sum(n => (long)n * 2);
    }

    static long SumWithLoop(IEnumerable<long> numbers) {
        long sum = 0;
        foreach (var n in numbers) {
            if (n > 0) sum += (long)n * 2;
        }

        return sum;
    }
}