using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    /*public static void Main(string[] args)

    { 

        Console.WriteLine("Please uncomment a test");

    }*/

    //*********************

    //*** Question 1

    //*** Describe the output of this program

    //*********************

    /*

    public static void Main(string[] args)

    { 

        int[] arr = new int[] {1 ,2 ,3 ,4 ,5 };

        fun1(ref arr);

        Console.ReadLine();

    }

    static void fun1(ref int[] array)

    {

        for (int i = 0; i < array.Length; i=i+2)

        {

            array[i] = array[i] + 10;

        }

        Console.WriteLine(string.Join(",", array));

    }

    */

    //*********************

    //*** Question 2

    //*** Describe the output of this program

    //*********************

    /*

    public static void Main(string[] args)

    {

        int num = 5;

        int square = 0, cube = 0;

        Mul (num, ref square, ref cube);

        Console.WriteLine(square + " & " +cube);

        Console.ReadLine();

    }

    static void Mul (int num, ref int square, ref int cube)

    {

        square = num * num;

        cube = num * num * num;

    }

    */

    //*********************

    //*** Question 3

    //*** Write a function that calculates a circle's circumference (Pi*radius*2)

    //*********************

    /*

    public static void Main()

    {

        Console.WriteLine("Enter the circle's radius");

        int radius = Convert.ToInt32(Console.ReadLine());

        double res = CalcCircumference(radius);

        Console.WriteLine("Circumference is: " + res);

    }

    static double CalcCircumference(int r) {

      //applicant's code goes here

    }

    */

    //*********************

    //*** Question 4

    //*** Write a program to check two given integers, and return true if one of them is 30 or if their sum is 30.

    //*********************

    /*

    public static void Main(string[] args)

    {

        Console.WriteLine(test(30, 0));

        Console.WriteLine(test(25, 5));

        Console.WriteLine(test(20, 30));

        Console.WriteLine(test(20, 25));

        Console.ReadLine();

    }

​

    public static bool test(int x, int y)

    {

        //applicant's code goes here

    }

    */

    //*********************

    //*** Question 5

    //*** Write a function to exchange the first and last characters in a given string and return the new string.

    //*********************

    /*

    public static void Main(string[] args)

    {

        Console.WriteLine(test("abc"));

        Console.WriteLine(test("abcdef"));

        Console.WriteLine(test("xy"));

        Console.WriteLine(test("x"));

    }

​

    public static string test(string str)

    {

        //applicant's code goes here

    }   

    */

    //*********************

    //*** Question 6

    //*** Write a program to print all unique elements in an array.

    //*********************

    /*

    public static void Main(string[] args)

    {

        int[] arr1 = new int[]{1, 1, 4, 3, 5, 3, 4, 6, 9, 9};

        var res = FindUniqueValues(arr1);

        Console.Write("\nThe unique elements found in the array are : \n");

        Console.Write(String.Join(",", res));

    }

    public static List<int> FindUniqueValues(int[] arr){

        //applicant's code goes here

        Dictionary<int,int> val =  new Dictionary<int,int>() ; 

        foreach(int ele in arr)

        {

            if(val.ContainsKey(ele))

            {

                val[ele]++;

            }

            else

            {

                val.Add(ele,1);

            }

        }

        return val.Where(x=>x.Value == 1).Select(x=>x.Key).ToList();

    }

    */

    //*********************

    //*** Question 7 (LINQ)

    //*** Write a function that finds and adds all the even numbers in the array

    //*********************

    /*

    public static void Main(int[] intArray) {

        int[] arr = new int[] {1 ,2 ,3 ,4 ,5 };

        long res = TotalAllEvenNumbers(arr);

        Console.WriteLine(res);

    }

    static long TotalAllEvenNumbers(int[] intArray) {

      //applicant's code goes here

    }

    */

    //*********************

    //*** Question 8 (LINQ)

    //*** Find which numbers in the array when squared are more than 20

    //*********************

    /*

    public static void Main(string[] args)

    {

        var arr1 = new[] { 3, 9, 2, 8, 6, 5 };      

        var res = FindAllNumbers(arr1);

        Console.WriteLine(String.Join(",", res));

    }

    static List<int> FindAllNumbers(int[] intArray) {

        //applicant's code goes here

    }   

    */

    //*********************

    //*** Question 9 (LINQ)

    //*** Write a program to display the characters and frequency of character from giving string.

    //*********************

​

    public class ResultObject{

        public Char Character {get; set;}

        public int Frequency {get; set;}

    }

    public static void Main(string[] args)

    {

        string str = "arkusnexus";          

        var res = FindAllFreq(str);

        Console.Write("The frequency of the characters are :\n");

        foreach(ResultObject item in res)  

        {  

            Console.WriteLine("Character "+item.Character + ": " + item.Frequency+" times");  

        }  

    }

    public static List<ResultObject> FindAllFreq(String str) {

        //applicant's code goes here

        var res = new List<ResultObject>();

        foreach(char ele in str)

        {

            if(res.Exists(x=>x.Character == ele))

            {

                res.Where(x=>x.Character == ele).First().Frequency ++;

            }

            else

            {

                res.Add(new ResultObject{

                    Character = ele,

                    Frequency = 1

                });

            }

        }

        return res;

    }

}