NetCalculator.cs

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

namespace NetCalculator
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] Input = @"193.253.23.143/25
85.14.23.132/25
215.54.233.12/30
193.253.23.200/25
192.168.23.214/24
193.253.23.150/1
85.14.23.232/30
85.14.23.132/1
193.253.23.22/24
193.253.23.22/24
85.14.23.32/24
32.177.34.244/25".Trim().Split('\n').Select((In) => In.Trim()).ToArray();

            List<uint> IPs = new List<uint>();

            for (int i = 0; i < 12; i++)
            {
                // Console.Write("Enter IP/Mask: ");
                string[] IPMask = Input[i].Trim().Split('/');
                uint IPInt = BitConverter.ToUInt32(IPAddress.Parse(IPMask[0]).GetAddressBytes().Reverse().ToArray(), 0);

                int BitNum = int.Parse(IPMask[1]);
                uint Mask = 0;

                if (BitNum != 0)
                    Mask = Convert.ToUInt32(new string('1', BitNum), 2);

                uint MaskedIP = (IPInt ^ Mask) >> BitNum;

                IPs.Add(MaskedIP);
            }

            for (int x = 0; x < IPs.Count; x++)
            {
                for (int y = 0; y < IPs.Count; y++)
                {
                    if (x == y)
                        continue;

                    if (IPs[x] == IPs[y])
                        Console.WriteLine("{0}. <-> {1}", x + 1, y + 1);
                }
            }

            Console.ReadLine();
        }
    }
}