chore(*): Move old solutions into a separate folder

old/2018/Day 01/Program.cs

@@ -0,0 +1,69 @@
+using System;
+using System.IO;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Day_01
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            //Part1();
+            Part2();            
+        }
+
+        static void Part1()
+        {
+            var frequency = 0;
+
+            var lines = File.ReadAllLines("input.txt");
+            foreach (var line in lines)
+            {
+                if (line.Substring(0,1) == "+") 
+                {
+                    frequency += Int32.Parse(line.Substring(1));
+                }
+                else 
+                {
+                    frequency -= Int32.Parse(line.Substring(1));
+                }
+            }
+            Console.WriteLine("Part 1: The resulting frequency is " + frequency);
+        }
+
+        static void Part2()
+        {
+            int frequency = 0;
+            List<int> frequencyHistory = new List<int>();
+            int loopCount = 0;
+            bool foundDuplicate = false;
+
+            var lines = File.ReadAllLines("input.txt");
+            while (!foundDuplicate) {
+                foreach (var line in lines)
+                {
+                    if (line.Substring(0,1) == "+") 
+                    {
+                        frequency += Int32.Parse(line.Substring(1));
+                    }
+                    else 
+                    {
+                        frequency -= Int32.Parse(line.Substring(1));
+                    }
+
+                    if (frequencyHistory.Contains(frequency)) {
+                        Console.WriteLine("The first repeated frequency is " + frequency);
+                        foundDuplicate = true;
+                        break;
+                    }
+                    else {
+                        frequencyHistory.Add(frequency);
+                    }
+                }
+                loopCount += 1;
+            }
+            Console.WriteLine("The loop count is " + loopCount);
+        }
+    }
+}