Add day 3

Day3/Day3.cs

@@ -0,0 +1,79 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+
+namespace Advent
+{
+    public static class Day3
+    {
+        public static void Execute()
+        {
+            var lines = File.ReadAllLines(@".\Day3\input.txt");
+
+            //lines[0] = "R75,D30,R83,U83,L12,D49,R71,U7,L72";
+            //lines[1] = "U62,R66,U55,R34,D71,R55,D58,R83";
+
+            //lines[0] = "R98,U47,R26,D63,R33,U87,L62,D20,R33,U53,R51";
+            //lines[1] = "U98,R91,D20,R16,D67,R40,U7,R15,U6,R7";
+
+            var spaces0 = GetWireSpaces(lines[0]);
+            var spaces1 = GetWireSpaces(lines[1]);
+
+            var intersections = spaces0.Keys.Intersect(spaces1.Keys).ToList();
+
+            var best = int.MaxValue;
+
+            foreach (var xy in intersections)
+            {
+                var distance = spaces0[xy] + spaces1[xy];
+
+                if (distance < best)
+                    best = distance;
+            }
+
+            Console.WriteLine($"{best}");
+        }
+
+        private static Dictionary<string, int> GetWireSpaces(string fullPath)
+        {
+            var x = 0;
+            var y = 0;
+            var steps = 1;
+
+            var usedSpaces = new Dictionary<string, int>();
+
+            foreach (var pathSegment in fullPath.Split(','))
+            {
+                var direction = pathSegment[0];
+                var count = int.Parse(pathSegment[1..]);
+
+                for (var i = 0; i < count; i++)
+                {
+                    switch (direction)
+                    {
+                        case 'U':
+                            y++;
+                            break;
+
+                        case 'D':
+                            y--;
+                            break;
+
+                        case 'L':
+                            x--;
+                            break;
+
+                        case 'R':
+                            x++;
+                            break;
+                    }
+
+                    usedSpaces[$"{x},{y}"] = steps++;
+                }
+            }
+
+            return usedSpaces;
+        }
+    }
+}