Course Work - C#

using System;

public class Program
{
    public static void Main()
    {
        //зад. 1
        //2025
        static void Main(string[] args)
        {
            int x = 2042;
            ConvertBinary(x);
            ConvertOctal(x);
            Console.WriteLine();
            Console.WriteLine("Hexadecimal: " + ConvertHexadecimal(x));
        }

        private static void ConvertBinary(int decimalNumber)
        {
            int remainder;
            string result = string.Empty;
            while (decimalNumber > 0)
            {
                remainder = decimalNumber % 2;
                decimalNumber /= 2;
                result = remainder.ToString() + result;
            }
            Console.WriteLine("Binary:  {0}", result);
        }
        private static void ConvertOctal(int decValue)
        {
            int counter, i = 1, j;
            int[] octalValue = new int[80];
            counter = decValue;
            while (counter != 0)
            {
                octalValue[i++] = counter % 8;
                counter /= 8;
            }
            Console.Write("Octal Number: ");
            for (j = i - 1; j > 0; j--)
                Console.Write(octalValue[j]);
        }
        private static string ConvertHexadecimal(int n)
        {
            if (n < 1) return "0";
            int hex = n;
            string hexStr = string.Empty;
            while (n > 0)
            {
                hex = n % 16;
                if (hex < 10)
                    hexStr = hexStr.Insert(0, Convert.ToChar(hex + 48).ToString());
                else
                    hexStr = hexStr.Insert(0, Convert.ToChar(hex + 55).ToString());
                n /= 16;
            }
            return hexStr;
        }

        //зад. 2
        //Тест 1 - 2 II)
            Console.Write("Enter B: ");
            int B = int.Parse(Console.ReadLine());
            Console.Write("Enter y:");
            int y = int.Parse(Console.ReadLine());
            Console.WriteLine((B + Math.Pow(Math.Sin(Math.Pow(Math.PI, 4)), 2)) / (Math.Pow(Math.Cos(6), ((double)1 / 5)) + Math.Abs((double)1 / Math.Tan(y))));

        //зад. 3
        //63
            Console.Write("Enter k: ");
            int k = int.Parse(Console.ReadLine());
            double y = -1;
            if (k == 1)
            {
            y = 6.7;
            }
            else if (k == 2)
            {
            y = 6.7 + 9 * k;
            }
            else if (k == 3)
            {
            y = 6.7 + 9 * k + 7 * Math.Pow(k, 2);
            }
            Console.WriteLine($"y = {y}");


        //зад. 4
        //213ж
            Console.WriteLine(TangensCalc(1));
            double TangensCalc(int v)
            {
            if (v == 100)
            {
                return Math.Tan(v);
            }
            return Math.Tan(v + TangensCalc(v + 1));
            }

        //зад. 5
        //379
            Random random = new Random();
            int[] arr = new int[132];
            for (int i = 0; i < arr.Length; i++)
            {
                arr[i] = (random.Next(0, 150));
            }
            for (int i = 0; i < arr.Length; i++)
            {
                if (arr[i] % 2 != 0)
                {
                    Console.WriteLine(arr[i]);
                }
            }

            Console.Write("Enter 5 numbers: ");
            int[] numbers = new int[5];
            string[] input = Console.ReadLine().Split(' ');
            for (int i = 0; i < numbers.Length; i++)
                numbers[i] = int.Parse(input[i]);
            int proizvedenie = numbers[0] * numbers[1] * numbers[2] * numbers[3] * numbers[4];
            Console.WriteLine(proizvedenie);
            double koren = (Math.Pow(proizvedenie, ((double)1 / 5)));
            Console.WriteLine(koren);

            Console.Write("Enter a= ");
            int a = int.Parse(Console.ReadLine());
            Console.Write("Enter b= ");
            int b = int.Parse(Console.ReadLine());
            Console.Write("Enter c= ");
            int c = int.Parse(Console.ReadLine());
            Console.WriteLine("Output is " + Sss(Math.Abs(c - b)) * Sss(a + c));
            BigInteger Sss(int k)
            {
                BigInteger product = 1;
                bool flag = true;
                Random r = new Random();
                for (int i = 0; i < k; i++)
                {
                    int a = r.Next(0, 100);
                    if ((a <= 99 && a >= 10) && a % 10 == 5)
                    {
                        flag = false;
                        product *= a;
                    }
                }
                if (flag)
                    return 0;
                else
                    return product;

            }

        //зад. 6
        //398
            Console.Write("Days in a month[1, 31]: ");
            int n = int.Parse(Console.ReadLine());
            while (n <= 0 && n > 31)
            {
            Console.WriteLine("Invalid days! Try again[1, 31]: ");
            n = int.Parse(Console.ReadLine());
            }
            Console.WriteLine("Station A");
            var stationA = Rains(n);
            Console.WriteLine("Station B");
            var stationB = Rains(n);
            Console.WriteLine("Station C");
            var stationC = Rains(n);
            double arithmeticA = Arithmetic(stationA);
            double arithmeticB = Arithmetic(stationB);
            double arithmeticC = Arithmetic(stationC);
            int overArithmeticA = 0, overArithmeticB = 0, overArithmeticC = 0;
            for (int i = 0; i < n; i++)
            {
            if (stationA[i] > arithmeticA)
            overArithmeticA++;
            if (stationB[i] > arithmeticB)
            overArithmeticB++;
            if (stationC[i] > arithmeticC)
            overArithmeticC++;
            }
            Console.WriteLine($"The Arithmetic of Station A is: {arithmeticA}! And has {overArithmeticA} days exceeding the arithmetic!");
            Console.WriteLine($"The Arithmetic of Station B is: {arithmeticB}! And has {overArithmeticB} days exceeding the arithmetic!");
            Console.WriteLine($"The Arithmetic of Station C is: {arithmeticC}! And has {overArithmeticC} days exceeding the arithmetic!");

            double Arithmetic(double[] days)
            {
            double sum = 0;
            int n = days.Length;
            for (int i = 0; i < n; i++)
            sum += days[i];
            return sum / n;
            }

            double[] Rains(int days)
            {
            double[] rains = new double[days];
            double n;
            for (int i = 0; i < days; i++)
            {
            Console.Write($"Day {i + 1}: ");
            n = double.Parse(Console.ReadLine());
            if (n >= 0)
            rains[i] = n;
            else
            i--;
            }
            Console.WriteLine();
            return rains;
            }

        //зад. 7
        //372аб
            static void Main(string[] args)
            {
            Console.Write("Въведете дължина на масива: ");
            int n = int.Parse(Console.ReadLine());
            while (n < 1 || n > 50)
            {
                Console.WriteLine("Дължината трябва да е между 1 и 50!");
                n = int.Parse(Console.ReadLine());
            }
            string[] cities = new string[n];
            InputElements(cities);
            Console.WriteLine("Градове съдържащи 'град' или 'Град' в името");
            StringContain(cities);
            }

            private static void StringContain(string[] cities)
            {
            string s1 = "град";
            string s2 = "Град";
            foreach (var item in cities)
            {
                if (item.Contains(s1) || item.Contains(s2))
                {
                    Console.WriteLine(item);
                }
            }
            }

            private static void InputElements(string[] cities)
            {
            for (int i = 0; i < cities.Length; i++)
            {
                Console.Write("Въведи град: ");
                string city = Console.ReadLine();
                cities[i] = FirstLetterToUpper(city);
            }
            }
            public static string FirstLetterToUpper(string str)
            {
            if (str == null)
                return null;
            else
                return char.ToUpper(str[0]) + str.Substring(1);
            }
    }
}