// In this solution, I used dictionary.

// First I divided the user input in all possible sub string of length equals to pattern length

// Then I stored these sub strings in dictionary called subStringDictionary as "Keys" and their respective values as intger '1'

// Before adding the sub string to the dictionary, checked whether dictionary already have stored that sub string as Key or not

// If yes the I retrieved the value of that Key value pair in integer variable, then removed that key value pair and then added that key value pair to dictionary again with value incremented by 1

// And at the end I itterated over the subStringDictionary and displayed the Key Value pairs whose Value is greater than 1

using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        startProgram();

    }

    public static void startProgram()

        {

            Console.WriteLine("Please enter the string");

            Console.WriteLine("String may contain any character");

            var input = Console.ReadLine();

            Console.WriteLine("String length: " + input.Length);

            Console.WriteLine("Please enter the pattern length");

            Console.WriteLine("Pattern length should be great than 1 and shorter than length of string you entred");

            var patternLength = Console.ReadLine();

            // If the entered pattern length is null

            // then program will ask the user to enter valid inputs

            // and startProgram() function will be called again

            if (patternLength == "")

            {

                Console.WriteLine("=============================");

                Console.WriteLine("Please enter the valid values");

                Console.WriteLine("=============================");

                startProgram();

                return;

            }

            // If entered input is null input or input length is less than pattern length

            // or entered pattern length is less than or equals to 1

            // then program will ask the user to enter valid inputs

            // and startProgram() function will be called again

​

            if (input == "" || input.Length <= Convert.ToInt32(patternLength) || Convert.ToInt32(patternLength) <= 1)

            {

                Console.WriteLine("You entered: ");

                Console.WriteLine("String: " + input);

                Console.WriteLine("Pattern Length: " + patternLength);

                Console.WriteLine("=============================");

                Console.WriteLine("Please enter the valid values");

                Console.WriteLine("=============================");

                startProgram();

                return;

​

​

            }

​

            usingDictionary(input, patternLength);        

         }

    static void usingDictionary(string input, string patternLengthStr)

        {

​

            int patternLength = Convert.ToInt32(patternLengthStr);

            var subStringDictionary = new Dictionary<string, int>();

            string subString;

            bool repeatingPatternOccured = false;

​

​

            // With following for loop I retrieved all sub strings of length equals to pattern length from input

            // and stored into subStringDictionary

​

            for (int i = 0; i < input.Length + 1 - patternLength; i++)

            {

                subString = "";

                for (int j = 0; j < patternLength; j++)

                {

                    subString = subString + input[i + j];

                }

                if (subStringDictionary.ContainsKey(subString))

                {

                    int count = subStringDictionary[subString];

                    subStringDictionary.Remove(subString);

                    subStringDictionary.Add(subString, count + 1);

                }

                else

                {

                    subStringDictionary.Add(subString, 1);

                }

​

            }

​

            Console.WriteLine("=============================");

            Console.WriteLine("Using dictionary");

            Console.WriteLine("=============================");

​

            // In following foreach loop I iterated over subStringDictionary

            // And displayed the Key value pairs whose Value is greater than 1

​

            foreach (var keyval in subStringDictionary)

            {

                if (keyval.Value > 1)

                {

                    repeatingPatternOccured = true;

                    Console.WriteLine("Repeated pattern: " + keyval.Key);

                    Console.WriteLine("Occurance value: " + keyval.Value);

                }

​

​

            }

            if (repeatingPatternOccured == false)

            {

                Console.WriteLine("There is no repeating pattern present");

            }

​

        }

}