From Wikipedia, the free encyclopedia:

 A happy number is defined by the following process:
 Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals   1   (where it will stay),   or it loops endlessly in a cycle which does not include   1.   


 Those numbers for which this process end in   1   are       happy   numbers,   
 while   those numbers   that   do   not   end in   1   are   unhappy   numbers. 


Task

Find and print the first   8   happy numbers.

Display an example of your output here on this page.



See also

   The OEIS entry:   The     happy numbers:   A007770
   The OEIS entry:   The unhappy numbers;   A031177


using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
 
namespace HappyNums
{
    class Program
    {
        public static bool ishappy(int n)
        {
            List<int> cache = new List<int>();
            int sum = 0;
            while (n != 1)
            {
                if (cache.Contains(n))
                {
                    return false;
                }
                cache.Add(n);
                while (n != 0)
                {
                    int digit = n % 10;
                    sum += digit * digit;
                    n /= 10;
                }
                n = sum;
                sum = 0;
            }
           return true;            
        }
 
        static void Main(string[] args)
        {
            int num = 1;
            List<int> happynums = new List<int>();
 
            while (happynums.Count < 8)
            {
                if (ishappy(num))
                {
                    happynums.Add(num);
                }
                num++;
            }
            Console.WriteLine("First 8 happy numbers : " + string.Join(",", happynums));
        }
    }
}