From 4a9a949d1ef28792e6066fbd60eff24d4f998d36 Mon Sep 17 00:00:00 2001
From: Alexander Sigler <asigler@costar.com>
Date: Mon, 11 Dec 2023 17:55:27 -0800
Subject: [PATCH] Completed Day 11 with optimized solution (no more giant 2d
 array)

---
 AdventOfCode/Common/AOCExtensions.cs |  12 +++
 AdventOfCode/_2023/Day11.cs          | 121 +++++++++++++++++++++------
 2 files changed, 109 insertions(+), 24 deletions(-)

diff --git a/AdventOfCode/Common/AOCExtensions.cs b/AdventOfCode/Common/AOCExtensions.cs
index f94411c..4b24299 100644
--- a/AdventOfCode/Common/AOCExtensions.cs
+++ b/AdventOfCode/Common/AOCExtensions.cs
@@ -57,5 +57,17 @@ namespace AdventOfCode.Common
                 Console.WriteLine();
             }
         }
+
+        public static void PrintSquareArray(this string[,] arr)
+        {
+            for (int x = 0; x < arr.GetLength(0); x++)
+            {
+                for (int y = 0; y < arr.GetLength(1); y++)
+                {
+                    Console.Write(arr[x, y] + " ");
+                }
+                Console.WriteLine();
+            }
+        }
     }
 }
diff --git a/AdventOfCode/_2023/Day11.cs b/AdventOfCode/_2023/Day11.cs
index fac36ac..c47e364 100644
--- a/AdventOfCode/_2023/Day11.cs
+++ b/AdventOfCode/_2023/Day11.cs
@@ -2,7 +2,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Threading.Tasks;
 
 namespace AdventOfCode._2023
 {
@@ -11,61 +10,135 @@ namespace AdventOfCode._2023
        
         protected override AOCResponse ExecutePartA()
         {
-           
-            return this._response;
+            return ExecutePartB();
         }
 
         protected override AOCResponse ExecutePartB()
         {
-           
+            //Determine how much space to replace each empty row with
+            var factor = this._request.Version == AOCVersion.A ? 2 : 1000000;
+
+            //Create our universe
+            var superUniverse = new SuperDuperUniverseGalaxy(factor, this.GetSplitInput().ToList());
+
+            var galaxies = superUniverse.Galaxies;
+
+            if (!this._request.IgnoreLogMessages)
+            {
+                foreach (var galaxy in galaxies)
+                {
+                    Console.WriteLine($"Galaxy {galaxy.Id} is at {galaxy.X},{galaxy.Y}");
+                }
+            }
+
+            //Calculate the shortest path.
+            long total = 0;
+            for (int i = 0; i < galaxies.Count; i++)
+            {
+                for (int j = i + 1; j < galaxies.Count; j++)
+                {
+                    total += galaxies[i].CalculateDistance(galaxies[j]);
+                }
+            }
+            this.Answer = total;
             return this._response;
         }
     }
 
-    class UniverseGalaxy
+    //AKA Part B
+    class SuperDuperUniverseGalaxy
     {
+        public List<Galaxy> Galaxies { get; set; }
         private string[,] _board;
-        public UniverseGalaxy(List<string> input)
+        public SuperDuperUniverseGalaxy(long factor, List<string> input)
         {
             var rows = input.Count;
             var columns = input.First().Length;
             _board = new string[rows, columns];
 
-            for (int y = 0; y < rows; y++)
+            for (int x = 0; x < rows; x++)
             {
-                for (int x = 0; x < columns; x++)
+                for (int y = 0; y < columns; y++)
                 {
                     _board[x, y] = input[x][y].ToString();
                 }
             }
 
-            //TODO Double the board
+            var doubledRows = GetDoubledRows();
+            var doubledColumns = GetDoubledColumns();
 
-            //TODO Find all the galaxies on the board
+            Galaxies = new List<Galaxy>();
+            int galaxyCount = 0;
+            for (int x = 0; x < _board.GetLength(0); x++)
+            {
+                for (int y = 0; y < _board.GetLength(1); y++)
+                {
+                    if (_board[x, y].Equals("#"))
+                    {
+                        long xOffset = doubledRows.Count(dR => dR <= x);
+                        long yOffset = doubledColumns.Count(dC => dC <= y);
+                        Galaxies.Add(new Galaxy()
+                        {
+                            Id = (++galaxyCount).ToString(),
+                            X = (xOffset * factor) + x - xOffset,
+                            Y = (yOffset * factor) + y - yOffset
+                        });
+                    }
+                }
+            }
+        }
 
-            //TODO Calculate the distance between all of the galaxies
+        public List<int> GetDoubledRows()
+        {
+            var doubledRows = new List<int>();
+            for (int x = 0; x < _board.GetLength(0); x++)
+            {
+                bool isEmpty = true;
+                for (int y = 0; y < _board.GetLength(1); y++)
+                {
+                    if (_board[x, y] == "#")
+                    {
+                        isEmpty = false;
+                        break;
+                    }
+                }
+                if (isEmpty)
+                    doubledRows.Add(x);
+            }
+            return doubledRows;
+        }
 
-            //TODO Find the shortest distance between them!
+        public List<int> GetDoubledColumns()
+        {
+            var doubledColumns = new List<int>();
+            for (int y = 0; y < _board.GetLength(1); y++)
+            {
+                bool isEmpty = true;
+                for (int x = 0; x < _board.GetLength(0); x++)
+                {
+                    if (_board[x, y] == "#")
+                    {
+                        isEmpty = false;
+                        break;
+                    }
+                }
+                if (isEmpty)
+                    doubledColumns.Add(y);
+            }
+            return doubledColumns;
         }
     }
 
     class Galaxy
     {
-        public Dictionary<string, long> DistanceLookup { get; set; }
         public string Id { get; set; }
-        public int X { get; set; }
-        public int Y { get; set; }
+        public long X { get; set; }
+        public long Y { get; set; }
 
-        public void CalculateDistance(IEnumerable<Galaxy> galaxies)
+        public long CalculateDistance(Galaxy galaxy)
         {
-            DistanceLookup = new Dictionary<string, long>();
-            foreach (var galaxy in galaxies)
-            {
-                if (galaxy.Id.Equals(this.Id)) continue;
-
-                long distanceBetweenGalaxies = -1; //TODO need to calculate this? some math.min and math.max
-                DistanceLookup[galaxy.Id] = distanceBetweenGalaxies;
-            }
+            //We use Manhattan distance |x2 - x1| + |y2-y1|
+            return Math.Abs(this.X - galaxy.X) + Math.Abs(this.Y - galaxy.Y);
         }
     }
 }