圈圈数字算法

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication16
{
    class Program
    {
        static void Main(string[] args)
        {
            int len = 6;
            for (int i = -20; i < 20; i++)
            {
                int n = ConvertCircleIndex(i, len);
                Console.WriteLine(i + " = " + n);
            }


            Console.ReadLine();
        }


        private static int ConvertCircleIndex(int index, int circlelen) 
        {
            if (index < 0)
            {
                index = Math.Abs(index);

                if (index > circlelen)
                    index = index % circlelen;

                index = (circlelen - index) % circlelen;
            }
            else
            {
                index = Math.Abs(index);
                index = index % circlelen;
            }
            return index; 
        }
    }
}