using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        //given a table of swimmer times for a single swimmer 

        var swimmers = new List<Swimmer>();

        for(int day = 0; day <= 365; day++)

        {

            swimmers.Add(new Swimmer() { Seconds = new Random(day).Next(200, 300), SwimDate = new DateTime(2015, 1, 1).AddDays(day) });

        }

        // #1 Print to the console each days swim time and the difference (delta) with the prior days swim time.  Use LINQ only for everything, including the printing to the console.

        string formatString = "Date: {0}, Time: {1}, Delta: {2}";

        swimmers

            .Take(1) // The first swim time doesn't have a previous, so set delta to "N/A"

            .Select(first =>

                    String.Format(formatString

                                  , first.SwimDate.ToString("MM/dd/yyyy")

                                  , first.Seconds

                                  , "  N/A"

                                 )

                   )

            .Union(

            swimmers.Skip(1) // Handle the rest of the swim times

            .Zip(swimmers, (cur, prev) => 

                 String.Format(formatString

                               , cur.SwimDate.ToString("MM/dd/yyyy")

                               , cur.Seconds

                               , (cur.Seconds - prev.Seconds).ToString().PadLeft(5)

                              )

                )

            )

            .ToList().ForEach(output =>  // ForEach is not part of Linq, but I'm not sure what else you would be looking for.

            {

                Console.WriteLine(output);

            });

        // #2 Print to the console the cumulative distribution of each days swim time to the swim times of all the points (using linq of course)

        // Sam Wehner:  The cumulative distribution is assumed to be the literal definition of a probability cumulative distribution, since this is the only

        // meaning of a cumulative distribution that I know of:  The running total divided by the grand total.

        double total = swimmers.Select(swimmer => swimmer.Seconds).Sum();

        double runningTotal = 0;

        swimmers

            .Select(swimmer =>

            {

                runningTotal += swimmer.Seconds;

                return String.Format("Date: {0}, Cumulative Distribution: {1:N5}"

                                     , swimmer.SwimDate.ToString("MM/dd/yyyy")

                                     , runningTotal / total);

            })

            .ToList().ForEach(output =>  // ForEach is not part of Linq, but I'm not sure what else you would be looking for.

            {

                Console.WriteLine(output);

            });

        // #3 Print to the console, using linq, a ranking of everyday for example:

            //#1  1/23/2015   201 seconds

            //#2  1/28/2015   205 seconds

        int rank = 0;

        int previousSeconds = int.MinValue;

        swimmers

            .OrderBy(swimmer => swimmer.Seconds)

            .ThenBy(swimmer => swimmer.SwimDate)

            .Select(swimmer =>

            {

                if(previousSeconds != swimmer.Seconds) // Check for ties

                {

                    rank++;

                }

                previousSeconds = swimmer.Seconds;

                return String.Format("#{0}  {1}   {2} seconds"

                                     , rank.ToString().PadLeft(3)

                                     , swimmer.SwimDate.ToString("MM/dd/yyyy")

                                     , swimmer.Seconds);

            })

            .ToList().ForEach(output =>  // ForEach is not part of Linq, but I'm not sure what else you would be looking for.

            {

                Console.WriteLine(output);

            });

    }

}

​

public class Swimmer

{

    public int Seconds { get; set; }

    public DateTime SwimDate { get; set; }

}