using System;

using System.Linq;

​

public class Program

{

    // Create methods for all 4 cases

​

    public static void Main()

    {

        // About arrays: http://msdn.microsoft.com/en-us/library/aa288453(v=vs.71).aspx

        int[] randomNumbers = GenerateRandomNumbers();

        // Example of foreach loop

        foreach(int number in randomNumbers)

        {

            Console.Write(number + ", ");

        }

        Console.WriteLine("");

        // 1. Should return number of 5 in the array. For instance, if array is [5, 3, 4, 5] then the result should be 2. 

        // Use for loop to solve it

        int countOfFifthInArray = CountFifth(randomNumbers);

        Console.WriteLine( "Quantity of number 5 - " + countOfFifthInArray);

        // 2. Should return number of items which are dividable on 2. For instance, 4/2 = 2 - correct, 5/2 = 2.5 - wrong.

        // Use while loop to solve it

        // hint: Use operator modulo. e.g. 3 - 3 % 2 > 0 therefore it is not devidable on 2

        int countOfNumberWhichAreDividableOnTwo = CountOfNumberWhichAreDividableOnTwo(randomNumbers);

        Console.WriteLine("Quantity of numbers which are dividable on 2 - " + countOfNumberWhichAreDividableOnTwo);

        // 3. Examples: 17 - OK, 14 - NO, 72 - OK

        // Use "do while" loop to solve it

        // You can conver number to string by calling ToString method on it. E.g. number.ToString().Contains(7)

        int countOfNumbersThatContainSeven = CountOfNumbersThatContainSeven(randomNumbers);

        Console.WriteLine("Quantity of numbers that contains 7 - " + countOfNumbersThatContainSeven);

        // 4. Change all even number to 0

        // Try all types of loops to solve it. 

        int[] arrayWithoutEvenNumbers = ChangeAllEvenNumbersToZero(randomNumbers);

        Console.WriteLine("Array without even numbers: ");

        foreach (int num in arrayWithoutEvenNumbers)

        {

            Console.Write(num + ", ");

        }

    }

    private static int[] ChangeAllEvenNumbersToZero(int[] array)

    {

        array = GenerateRandomNumbers();

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

        {

            if (array[i] % 2 == 0)

            {

                array[i] = 0;

            }

        }

        return array;

    }

    private static int CountOfNumbersThatContainSeven(int[] array)

    {

        array = GenerateRandomNumbers();

        int countItemsThatContainSeven = 0;

        int i = 0;

        do 

        {

            if (array[i].ToString().Contains("7")== true)

            {

                countItemsThatContainSeven++;

            }

            i++;

        }while (i < array.Length);

        return countItemsThatContainSeven;

    }

    private static int CountOfNumberWhichAreDividableOnTwo(int[] array)

    {

        array = GenerateRandomNumbers();

        int countDividableNumbers = 0;

        int i = 0;

        while (i < array.Length)

        {

            if (array[i]%2 == 0) 

            {

                countDividableNumbers++;

            }

         i++;

        }

        return countDividableNumbers;

    }

    private static int CountFifth(int[] array) 

    {

        array = GenerateRandomNumbers();

        int countItemsInArray = 0;

        foreach (int num in array)

        {

            if (num == 5) 

            {

                countItemsInArray++;

            }   

        }

        return countItemsInArray;

    }

    // It is helper method. Do not change it.

    private static int[] GenerateRandomNumbers()

    {

        var random = new Random();

        return (new int[20]).Select(i=> i = random.Next(20)).ToArray();

    }

}