Day 15 part 2

AoC2018.Runner/Properties/launchSettings.json

@@ -2,7 +2,7 @@
   "profiles": {
     "AoC2018.Runner": {
       "commandName": "Project",
-      "commandLineArgs": "15 1"
+      "commandLineArgs": "15 2"
     }
   }
 }

AoC2018.Solutions/Day15/MapSpaceExtensions.cs

@@ -1,5 +1,7 @@
 namespace AoC2018.Solutions.Day15
 {
+    using System.Linq;
+
     public static class MapSpaceExtensions
     {
         public static bool IsEmpty(this MapSpace space)

AoC2018.Solutions/Day15/Part02.cs

@@ -0,0 +1,60 @@
+using System;
+
+namespace AoC2018.Solutions.Day15
+{
+    public class Part02 : ISolution
+    {
+        public string Solve(string input)
+        {
+            ////Console.WriteLine(currentState.ToString());
+
+            int attackStrength = 4;
+
+            while (true)
+            {
+                ////Console.WriteLine($"Running with hit points = {attackStrength}");
+
+                var currentState = State.Parse(input);
+                Elf[] elves = currentState.GetUnits<Elf>();
+                int elfCount = elves.Length;
+
+                // Set their hit count
+                foreach (Elf current in elves)
+                {
+                    current.AttackStrength = attackStrength;
+                }
+
+                int rounds = 0;
+                bool deadElves = false;
+
+                while (!deadElves)
+                {
+                    bool roundCompleted = currentState.Round();
+
+                    if (roundCompleted)
+                    {
+                        rounds++;
+                    }
+
+                    deadElves = currentState.CountUnits<Elf>() < elfCount;
+
+                    if (currentState.IsCombatEnded())
+                    {
+                        break;
+                    }
+                }
+
+                if (deadElves)
+                {
+                    ////Console.WriteLine($"Elves died during round {rounds}");
+                    attackStrength++;
+                }
+                else
+                {
+                    return (rounds * currentState.TotalRemainingHitPoints()).ToString();
+                }
+            }
+
+        }
+    }
+}

AoC2018.Solutions/Day15/StateExtensions.cs

@@ -64,5 +64,17 @@ public static int TotalRemainingHitPoints(this State state)
         {
             return state.Map.Sum(x => x?.Unit?.HitPoints ?? 0);
         }
+
+        public static int CountUnits<T>(this State state)
+            where T : Unit
+        {
+            return state.Map.Count(x => x?.Unit?.GetType() == typeof(T));
+        }
+
+        public static T[] GetUnits<T>(this State state)
+            where T : Unit
+        {
+            return state.Map.Where(x => x?.Unit?.GetType() == typeof(T)).Select(x => (T)x.Unit).ToArray();
+        }
     }
 }