using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

       try

        {

            var patterns = FindAllPatterns("zfabcde224lkfabc51+crsdtab=", 3);

            PrintAllPatterns(patterns);

        }

        catch (Exception ex)

        {

            Console.WriteLine(ex);

        }     

    }

    static List<Pattern> FindAllPatterns(string input, int patternLength)

    {

        InputValidation(input, patternLength);

​

        List<Pattern> listOfPatterns = new List<Pattern>();

        Dictionary<string, int> temp = new Dictionary<string, int>();

​

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

        {

            bool cannotFormPattern = (i + patternLength - 1) > input.Length - 1;

            if (cannotFormPattern){ break; }

            string pattern = input.Substring(i, patternLength);

            temp[pattern] = temp.ContainsKey(pattern) ? temp[pattern] + 1 : 1;

        }

​

        if (temp.Count > 1)

        {

            foreach (var item in temp)

            {

                if (temp[item.Key] > 1)

                {

                    listOfPatterns.Add(new Pattern(item.Key, item.Value));

                }

            }

        } else

        {

            foreach (var item in temp)

            {

                listOfPatterns.Add(new Pattern(item.Key, item.Value));

            }

        }

​

        return listOfPatterns;

    }

​

    static void InputValidation(string input, int patternLength)

    {

        if (patternLength > input.Length - 1 || patternLength == 0 || input == string.Empty)

        {

            throw new NullReferenceException("invalid values entered...");

        }

    }

​

    static void PrintAllPatterns(List<Pattern> patterns)

    {

        if (patterns.Count > 1)

        {

            foreach (var pattern in patterns)

            {

                Console.WriteLine("pattern: " + pattern.Value + "\nnumber of occurance: " + pattern.Occurances);

            }

        } else

        {

            Console.WriteLine("There are no patterns that occured more than once...");

        }

    }

}

​

class Pattern

{

    public string Value { get; set; }

    public int Occurances { get; set; }

​

    public Pattern(string value, int occurances)

    {

        this.Value = value;

        this.Occurances = occurances;

    }

}