//AMEN-AMEN, MA. SARAH

//VILLABROZA, HANSSELL D.

//CCP 1103 - ITDC

//HAPPY NUMBER

​

using System;                    

public class Program 

{  

    public static void Main(string[] args)

    {

            string answer;

​

            do

            {

                string inputNumber;

                int sum = 0;

                int digit;

                int number;

​

                Console.Clear();

                Console.WriteLine("Happy Numbers");

                Console.WriteLine();

​

                Console.Write("Enter a number: ");

                inputNumber = Console.ReadLine();

                if (Int32.TryParse(inputNumber, out number) == true)

                {

                    if (number <= 0)

                    {

                        Console.WriteLine("Zero or negative input is not allowed.");

                    }

                    else if (number > 20000)

                    {

                        Console.WriteLine("Invalid input. Please input 1-20,000 only.");

                    }

                    else

                    {

                        for (int i = 1; i <= 50; i++)

                        {

                            sum = 0;

                            while (number >= 10)

                            {

                                digit = number % 10;

                                sum += digit * digit;

                                number /= 10;

                            }

​

                            sum += number * number;

​

                            if (sum == 1)

                            {

                                i = 50;

                            }

                            else

                            {

                                number /= 10;

                                while (number < 10)

                                {

                                    sum += number * number;

                                    number = sum;

                                }

                            }

​

                        }

                        if (number == 1)

                        {

                            Console.WriteLine(inputNumber + " is a happy number.");

                        }

                        else

                        {

                            Console.WriteLine(inputNumber + " is not a happy number.");

                        }

                    }

                }

                else

                {

                    Console.WriteLine("Invalid Input. Please Enter a numeric value.");

                }

​

                Console.WriteLine();

                Console.Write("Do you want to try again [Y/y]? ");

                answer = Console.ReadLine();

​

            } while ((answer == "Y") || (answer == "y"));

​

            Console.WriteLine("End of the program. Press any key to exit...");

     }

}