using System;

using System.Collections.Generic;

using System.Linq;

​

/* 

Author- Taruna Verma

What to expect - 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. 

​

For example, when searching the string "zf3kabxcde224lkzf3mabxc51+crsdtzf3nab=", with a specified pattern length of 3, 

the method should return the pattern "abx” with an occurrence value of two, and “zf3” with an occurrence value of three.

​

Assumptions -

1. Input string length does not exceed the max size of string

2. Space, special characters, unicodes and digits are treated as part of pattern like regular characters,

they are not identified as special case

3. Pattern length does not exceed the max size of Int32

​

Input Validations - 

1. Pattern Length > 0

2. Pattern Lenth < length of InputString

3. Input string should not be empty

​

Scope for future development

1. Special characters case - user to choose whether special character need to be part of pattern. - Ignore special characters

2. Digits case - user to choose whether digits need to be part of pattern. - Ignore digits

3. Identify unicodes and their patterns.

​

*/

​

public class FrozenMountain

{   

    // Splitting an input string into an array of a pattern length

    static public IEnumerable<string> ConvertStringToArraySize(string sInputString, int nPatternLength)

    {

        for (int index = 0; index <= sInputString.Length - nPatternLength; index++)

        {

            yield return sInputString.Substring(index, nPatternLength);         

        }

    }

​

    // Find the patterns of specified length and their occurences

    static public Dictionary<string,int> Pattern_Finder_Count(string sInputString, int nPatternLength, string sCase)

    {

        if (nPatternLength <= 0)

        {

            throw new ArgumentException("Pattern length should be greater than '0'","nPatternLength");

        }

​

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

        {

            throw new ArgumentException("Input string can not be null or empty.","sInputString");

        }

​

        if (nPatternLength > sInputString.Length)

        {

            throw new ArgumentException("Pattern length can not be greater than input string length", "nPatternLength");

        }

​

        // Splitting an input string into an array of a pattern length

        var result = ConvertStringToArraySize(sInputString, nPatternLength);        

        StringComparer ignoreCase = StringComparer.InvariantCulture;

        if( sCase.Equals("y") || sCase.Equals("Y")) // ignore case 

            ignoreCase = StringComparer.InvariantCultureIgnoreCase;

        // group by pattern and return the patterns and their counts if occurences is greater than 1

        return result.GroupBy(x => x, ignoreCase).Where(gr => gr.Count()>1).ToDictionary(gr => gr.Key, gr => gr.Count());

    }

​

    public static void Main()

    {

        Console.WriteLine("Enter an input string");

        string sInputString = Console.ReadLine();       

​

        Console.WriteLine("Ignore case sensitive [y/n]");

        string sCase = Console.ReadLine();      

​

        Console.WriteLine("Enter a pattern length");

        int nPatternLength;

​

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

        {

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

            patterns = Pattern_Finder_Count(sInputString, nPatternLength, sCase);

            if(patterns.Count > 0)

            {

                foreach(KeyValuePair<string, int> pattern in patterns)

                {

                    Console.WriteLine("Pattern : " + pattern.Key.ToString() + "  -  Occurence: " + pattern.Value.ToString());

                }

            }

            else Console.WriteLine("There are no patterns of length "+ nPatternLength);

        }

        else Console.WriteLine("Input length is not a valid number");

        Console.ReadLine();

    }

}