Adv2018/D1.2/Program.cs

using System;
using System.Collections.Generic;
using System.IO;

namespace D1._2
{
    class Program
    {
        static void Main(string[] args)
        {
            if (args.Length < 1) return;
            if (File.Exists(args[0]) == false) return;

            var frequencies = new Dictionary<int, bool>()
            {
                { 0, true }
            };
            int frequency = 0;

            bool foundTwice = false;
            do
            {
                var file = File.OpenText(args[0]);
                foundTwice = ApplySequence(frequencies, ref frequency, ref foundTwice, file);
                file.Close();
            } while (foundTwice == false);

            if (foundTwice) Console.WriteLine($"Result : {frequency}");
        }

        private static bool ApplySequence(Dictionary<int, bool> frequencies, ref int frequency, ref bool foundTwice, StreamReader file)
        {
            do
            {
                var line = file.ReadLine();
                if (line == null) break;

                frequency += int.Parse(line);

                if (frequencies.ContainsKey(frequency)) foundTwice = true;
                else frequencies.Add(frequency, true);
            } while (foundTwice == false);

            return foundTwice;
        }
    }
}