From 16053d1a513d1993fc492aa2458b2e511ce155a4 Mon Sep 17 00:00:00 2001
From: Smaug123 <patrick+github@patrickstevens.co.uk>
Date: Mon, 11 Dec 2023 08:49:36 +0000
Subject: [PATCH] Day 11 part 2

---
 .../AdventOfCode2023.FSharp.Lib/Day11.fs      | 56 ++++++++++++-------
 AdventOfCode2023.FSharp/Test/TestDay11.fs     | 11 ++--
 2 files changed, 42 insertions(+), 25 deletions(-)

diff --git a/AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/Day11.fs b/AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/Day11.fs
index 6c8c4d6..4fde534 100644
--- a/AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/Day11.fs
+++ b/AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/Day11.fs
@@ -5,17 +5,17 @@ open System
 [<RequireQualifiedAccess>]
 module Day11 =
 
-    let inline private toRowAndCol (lineLength : int) (pos : int) : struct (int * int) =
-        let lineNum = pos / lineLength
-        let withinLine = pos % lineLength
-        struct (lineNum, withinLine)
+    type Data =
+        {
+            RowsWithoutGalaxies : ResizeArray<int>
+            ColsWithoutGalaxies : ResizeArray<int>
+            /// row * col
+            Galaxies : ResizeArray<int * int>
+        }
 
-    let inline private ofRowAndCol (lineLength : int) (lineNum : int) (col : int) : int = lineNum * lineLength + col
-
-    let part1 (s : string) =
+    let parse (s : string) : Data =
         let galaxies = ResizeArray ()
         let rowsWithoutGalaxies = ResizeArray ()
-        let rowLength = s.IndexOf '\n'
         let mutable hasAnyGalaxy = false
         let mutable currRowIndex = 0
         let mutable currColIndex = 0
@@ -50,25 +50,32 @@ module Day11 =
 
             result
 
-        let mutable answer = 0
+        {
+            RowsWithoutGalaxies = rowsWithoutGalaxies
+            ColsWithoutGalaxies = colsWithoutGalaxies
+            Galaxies = galaxies
+        }
 
-        for galaxy1 = 0 to galaxies.Count - 1 do
-            let row1, col1 = galaxies.[galaxy1]
+    let solve (data : Data) (expansion : uint64) =
+        let mutable answer = 0uL
 
-            for galaxy2 = galaxy1 + 1 to galaxies.Count - 1 do
-                let row2, col2 = galaxies.[galaxy2]
-                let baseDistance = abs (row1 - row2) + abs (col1 - col2)
+        for galaxy1 = 0 to data.Galaxies.Count - 1 do
+            let row1, col1 = data.Galaxies.[galaxy1]
+
+            for galaxy2 = galaxy1 + 1 to data.Galaxies.Count - 1 do
+                let row2, col2 = data.Galaxies.[galaxy2]
+                let baseDistance = uint64 (abs (row1 - row2) + abs (col1 - col2))
 
                 let extraDistance =
-                    let mutable extraDistance = 0
+                    let mutable extraDistance = 0uL
 
                     for i = 1 + min row1 row2 to max row1 row2 - 1 do
-                        if rowsWithoutGalaxies.Contains i then
-                            extraDistance <- extraDistance + 1
+                        if data.RowsWithoutGalaxies.Contains i then
+                            extraDistance <- extraDistance + expansion - 1uL
 
                     for i = 1 + min col1 col2 to max col1 col2 - 1 do
-                        if colsWithoutGalaxies.Contains i then
-                            extraDistance <- extraDistance + 1
+                        if data.ColsWithoutGalaxies.Contains i then
+                            extraDistance <- extraDistance + expansion - 1uL
 
                     extraDistance
 
@@ -76,6 +83,13 @@ module Day11 =
 
         answer
 
+
+    let part1 (s : string) =
+        let data = parse s
+
+        solve data 2uL
+
     let part2 (s : string) =
-        use s = StringSplitEnumerator.make '\n' s
-        0
+        let data = parse s
+
+        solve data 1_000_000uL
diff --git a/AdventOfCode2023.FSharp/Test/TestDay11.fs b/AdventOfCode2023.FSharp/Test/TestDay11.fs
index ffc65c6..3fad587 100644
--- a/AdventOfCode2023.FSharp/Test/TestDay11.fs
+++ b/AdventOfCode2023.FSharp/Test/TestDay11.fs
@@ -12,10 +12,13 @@ module TestDay11 =
 
     [<Test>]
     let part1Sample () =
-        sample |> Day11.part1 |> shouldEqual 374
+        sample |> Day11.part1 |> shouldEqual 374uL
 
     [<Test>]
-    let part2Sample () = sample |> Day11.part2 |> shouldEqual -1
+    let part2Sample () =
+        let data = sample |> Day11.parse
+        Day11.solve data 10uL |> shouldEqual 1030uL
+        Day11.solve data 100uL |> shouldEqual 8410uL
 
     [<Test>]
     let part1Actual () =
@@ -28,7 +31,7 @@ module TestDay11 =
                 Assert.Inconclusive ()
                 failwith "unreachable"
 
-        Day11.part1 s |> shouldEqual 9947476
+        Day11.part1 s |> shouldEqual 9947476uL
 
     [<Test>]
     let part2Actual () =
@@ -41,4 +44,4 @@ module TestDay11 =
                 Assert.Inconclusive ()
                 failwith "unreachable"
 
-        Day11.part2 s |> shouldEqual -1
+        Day11.part2 s |> shouldEqual 519939907614uL