using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Example1:");

        var result1 = FindPatterns("a12v89fsdseef8a7sd7v7aussdshdf7v7b89s8d9q6q8a74sds", 3);

        foreach(var r in result1){

            Console.WriteLine(r.Item1 + " " + r.Item2);

        }

        Console.WriteLine();

        Console.WriteLine("Example2:");

        var result2 = FindPatterns("aaaaaaaaaaaaaaaa", 4);

        foreach(var r in result2){

            Console.WriteLine(r.Item1 + " " + r.Item2);

        }

    }

    public static List<Tuple<string, int>> FindPatterns(string input,  int length)

    {

        List<string> sl = new List<String>();

        for (int i=0 ; i <= input.Length-length; i++)

        {

            sl.Add(input.Substring(i, length));

        }

        //find all substrings with the length and add them to a list

​

        var result = from s in sl 

                        group s by s into g

                        where g.Count() > 1

                        select new Tuple<string, int>(g.Key,g.Count());

        //use linq to find all substrings that occur more than once, add the patterns and the number occurrences to a list of tuples

​

        return result.ToList();

    }

}