using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;

namespace ElementAtOrIndex
{
    class Program
    {
        // Declare/initialize static variables.
        static Stopwatch timer = new Stopwatch();
        static List<long> ElementAtTimes = new List<long>();
        static List<long> IndexTimes = new List<long>();

        static void Main(string[] args)
        {
            // Declare/initialize variables.
            int[] array;
            int count = 1000000;
            int iterations = 100;

            // Just initializes a list with elements from 0 to count.
            // Slower than for loops, but pithy for an example on SO.
            List<int> list = Enumerable.Range(0, count).ToList<int>();
            
            // Assert that both methods are equal.
            for (int i = 0; i < list.Count; i++)
            {
                if (list.ElementAt(i) != list[i])
                {
                    Console.WriteLine("Both methods are not equal!");
                    Environment.Exit(1);
                }
            }
            Console.WriteLine("Both methods are equal!");

            // Time ElementAt access *iterations* times by copying into an array.
            for (int i = 0; i < iterations; i++)
            {
                // [Re]initialize the array.
                array = new int[count];

                // Start the timer.
                timer.Start();

                for (int j = 0; j < list.Count; j++)
                    array[j] = list.ElementAt(j);

                // Explicitly stop the timer.
                timer.Stop();

                // Note the time. 
                ElementAtTimes.Add(timer.ElapsedMilliseconds);
	        timer.Reset();
            }

	    timer.Reset();

            // Time Index access *iterations* times by copying into an array.
            for (int i = 0; i < iterations; i++)
            {
                // [Re]initialize the array.
                array = new int[count];

                // Start the timer.
                timer.Start();

                for (int j = 0; j < list.Count; j++)
                    array[j] = list[j];

                // Explicitly stop the timer.
                timer.Stop();

                // Note the time. 
                IndexTimes.Add(timer.ElapsedMilliseconds);
                timer.Reset();
            }

            // Output times.
            Console.WriteLine("Average time for ElementAt access iteration: {0} ms", ElementAtTimes.Average());
            Console.WriteLine("Average time for Index access iteration: {0} ms", IndexTimes.Average());

            Console.ReadLine();
        }
    }
}