/*

Write a program that takes these values to find all of the different patterns in "input" of length "patternLength"

and output all of the patterns that occur more than once and the number of times they occur.

*/

​

using System;

using System.Collections.Generic;

using System.Linq;

​

​

public class PatternCount

{

    public string Pattern { get; set; }

    public int Count { get; set; }

}

public class PatternFinder

{

    /* Assumptions:

            1. input string should not be longer than 32 characters.

            2. String can only have printable ASCII-equivalent characters.

            3. Pattern Length should be greater than 0 but not more than 32 characters. 

    */

    public static IEnumerable<string> GetChunks(string input, int size)

    {

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

        {

            yield return input.Substring(i, size);

        }

    }

    /*

    Returns a dictionary containg patterns and the number of times they appear

    */

    public static List<PatternCount> FilterAndCountPatterns(string input, int patternLength, int minMatchCount)

    {

        if(patternLength <= 0)

        {

            throw new ArgumentOutOfRangeException(String.Format("Expected Pattern should be greater than 0 but got {0} here.", patternLength));

        }

        if(input == null || input.Length == 0)

        {

            throw new ArgumentException("Expected input string cannot be empty.");

        }

        var patternQuery = from pattern in GetChunks(input, patternLength)

            group pattern by pattern into patternGroup

            where patternGroup.Count() >= minMatchCount

            select new PatternCount{ Pattern = patternGroup.Key, Count = patternGroup.Count() };

        return patternQuery.ToList();

    }

​

    public static void Main()

    {

        var minMatchCount = 2;

        Console.WriteLine("Enter a string:");

        var inputString = Console.ReadLine();

        Console.WriteLine("Enter Pattern Length:");

        int patternLength;

        if(int.TryParse(Console.ReadLine(), out patternLength))

        {

            var results = PatternFinder.FilterAndCountPatterns(inputString, patternLength, minMatchCount);

            if(results.Count() == 0){

            Console.WriteLine("No patterns found with the entered input.");

            }else{

                Console.WriteLine(String.Format("Found the following patterns with at least {0} matches:", minMatchCount));

                foreach(var item in results)

                {

                    Console.WriteLine(String.Format("{0} -> {1}", item.Pattern, item.Count));

                }

            }

        }

        else

        {

            Console.WriteLine("Please enter a valid number for Pattern Length");

        }

        Console.WriteLine("Press any key to exit");

        Console.ReadLine();

    }

}