Day 11 part 1

AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/AdventOfCode2023.FSharp.Lib.fsproj

@@ -21,6 +21,7 @@
     <Compile Include="Day8.fs"/>
     <Compile Include="Day9.fs"/>
     <Compile Include="Day10.fs" />
+    <Compile Include="Day11.fs" />
   </ItemGroup>
 
 </Project>

AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/Day11.fs

@@ -0,0 +1,81 @@
+namespace AdventOfCode2023
+
+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)
+
+    let inline private ofRowAndCol (lineLength : int) (lineNum : int) (col : int) : int = lineNum * lineLength + col
+
+    let part1 (s : string) =
+        let galaxies = ResizeArray ()
+        let rowsWithoutGalaxies = ResizeArray ()
+        let rowLength = s.IndexOf '\n'
+        let mutable hasAnyGalaxy = false
+        let mutable currRowIndex = 0
+        let mutable currColIndex = 0
+
+        for c in s do
+            if c = '\n' then
+                if not hasAnyGalaxy then
+                    rowsWithoutGalaxies.Add currRowIndex
+
+                currRowIndex <- currRowIndex + 1
+                currColIndex <- 0
+                hasAnyGalaxy <- false
+            elif c = '#' then
+                hasAnyGalaxy <- true
+                galaxies.Add (currRowIndex, currColIndex)
+                currColIndex <- currColIndex + 1
+            else
+                currColIndex <- currColIndex + 1
+
+        galaxies.Sort (fun (_, c1) (_, c2) -> compare c1 c2)
+
+        let colsWithoutGalaxies =
+            let result = ResizeArray ()
+            let mutable prevCol = 0
+
+            for (_, c) in galaxies do
+                if c > prevCol then
+                    for j = prevCol + 1 to c - 1 do
+                        result.Add j
+
+                    prevCol <- c
+
+            result
+
+        let mutable answer = 0
+
+        for galaxy1 = 0 to galaxies.Count - 1 do
+            let row1, col1 = galaxies.[galaxy1]
+
+            for galaxy2 = galaxy1 + 1 to galaxies.Count - 1 do
+                let row2, col2 = galaxies.[galaxy2]
+                let baseDistance = abs (row1 - row2) + abs (col1 - col2)
+
+                let extraDistance =
+                    let mutable extraDistance = 0
+
+                    for i = 1 + min row1 row2 to max row1 row2 - 1 do
+                        if rowsWithoutGalaxies.Contains i then
+                            extraDistance <- extraDistance + 1
+
+                    for i = 1 + min col1 col2 to max col1 col2 - 1 do
+                        if colsWithoutGalaxies.Contains i then
+                            extraDistance <- extraDistance + 1
+
+                    extraDistance
+
+                answer <- answer + extraDistance + baseDistance
+
+        answer
+
+    let part2 (s : string) =
+        use s = StringSplitEnumerator.make '\n' s
+        0