Day 16 (#18)

Co-authored-by: Smaug123 <patrick+github@patrickstevens.co.uk>
Reviewed-on: #18

AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Bench/Inputs.fs

@@ -14,6 +14,6 @@ module Inputs =
             if isNull dir then
                 failwith "reached root of filesystem without finding inputs dir"
 
-        Array.init 15 (fun day -> Path.Combine (dir.FullName, "inputs", $"day%i{day + 1}.txt") |> File.ReadAllText)
+        Array.init 16 (fun day -> Path.Combine (dir.FullName, "inputs", $"day%i{day + 1}.txt") |> File.ReadAllText)
 
     let inline day (i : int) = days.[i - 1]

AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Bench/Program.fs

@@ -57,6 +57,23 @@ module Benchmarks =
         [<GlobalCleanup>]
         member _.Cleanup () = Run.shouldWrite <- true
 
+    type Benchmark16To20 () =
+        [<GlobalSetup>]
+        member _.Setup () = Run.shouldWrite <- false
+
+        [<Params(16)>]
+        member val Day = 0 with get, set
+
+        [<Params(false, true)>]
+        member val IsPartOne = false with get, set
+
+        [<Benchmark>]
+        member this.Benchmark () : unit =
+            Run.allRuns.[this.Day - 1] (not this.IsPartOne) (Inputs.day this.Day)
+
+        [<GlobalCleanup>]
+        member _.Cleanup () = Run.shouldWrite <- true
+
 module Program =
 
     [<EntryPoint>]

AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Bench/Run.fs

@@ -209,6 +209,18 @@ module Run =
             if shouldWrite then
                 Console.WriteLine output
 
+    let day16 (partTwo : bool) (input : string) =
+        if not partTwo then
+            let output = Day16.part1 input
+
+            if shouldWrite then
+                Console.WriteLine output
+        else
+            let output = Day16.part2 input
+
+            if shouldWrite then
+                Console.WriteLine output
+
     let allRuns =
         [|
             day1
@@ -226,4 +238,5 @@ module Run =
             day13
             day14
             day15
+            day16
         |]

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

@@ -3,6 +3,7 @@
   <PropertyGroup>
     <TargetFramework>net8.0</TargetFramework>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>
 
   <ItemGroup>
@@ -26,6 +27,7 @@
     <Compile Include="Day13.fs" />
     <Compile Include="Day14.fs" />
     <Compile Include="Day15.fs" />
+    <Compile Include="Day16.fs" />
   </ItemGroup>
 
 </Project>

AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/Day16.fs

@@ -0,0 +1,297 @@
+namespace AdventOfCode2023
+
+#if DEBUG
+#else
+#nowarn "9"
+#endif
+
+open System
+
+[<RequireQualifiedAccess>]
+module Day16 =
+
+    type Direction =
+        | Left = 0
+        | Right = 1
+        | Up = 2
+        | Down = 3
+
+    let inline dirToInt (d : Direction) =
+        match d with
+        | Direction.Left -> 0us
+        | Direction.Right -> 1us
+        | Direction.Up -> 2us
+        | Direction.Down -> 3us
+        | _ -> failwith "Bad"
+
+    let inline storeDirectionAndPos (numCols : int) (col : int) (row : int) (direction : Direction) : uint16 =
+        4us * uint16 (col + numCols * row) + dirToInt direction
+
+    let inline getDirection (input : uint16) =
+        match input % 4us with
+        | 0us -> Direction.Left
+        | 1us -> Direction.Right
+        | 2us -> Direction.Up
+        | 3us -> Direction.Down
+        | _ -> failwith "bad"
+
+    let inline getCol (numCols : int) (input : uint16) = (input / 4us) % uint16 numCols |> int
+
+    let inline getRow (numCols : int) (input : uint16) = (input / 4us) / uint16 numCols |> int
+
+    let inline maxEncoded (numCols : int) (numRows : int) : uint16 =
+        4us * uint16 ((numCols - 1) + numCols * (numRows - 1)) + 3us
+
+    let inline getAt (numCols : int) (s : string) (row : int) (col : int) = s.[row * (numCols + 1) + col]
+
+    let advance (arr : Arr2D<_>) (going : ResizeArray<_>) (s : string) (nextUp : uint16) =
+        let numCols = arr.Width
+        let numLines = arr.Height
+        let col = getCol numCols nextUp
+        let row = getRow numCols nextUp
+        let dir = getDirection nextUp
+        Arr2D.set arr col row true
+
+        match dir with
+        | Direction.Right ->
+            match getAt numCols s row col with
+            | '-'
+            | '.' ->
+                if col < arr.Width - 1 then
+                    going.[going.Count - 1] <- storeDirectionAndPos numCols (col + 1) row dir
+                else
+                    going.RemoveAt (going.Count - 1)
+            | '/' ->
+                if row > 0 then
+                    going.[going.Count - 1] <- storeDirectionAndPos numCols col (row - 1) Direction.Up
+                else
+                    going.RemoveAt (going.Count - 1)
+            | '\\' ->
+                if row < numLines - 1 then
+                    going.[going.Count - 1] <- storeDirectionAndPos numCols col (row + 1) Direction.Down
+                else
+                    going.RemoveAt (going.Count - 1)
+            | '|' ->
+                going.RemoveAt (going.Count - 1)
+
+                if row < numLines - 1 then
+                    going.Add (storeDirectionAndPos numCols col (row + 1) Direction.Down)
+
+                if row > 0 then
+                    going.Add (storeDirectionAndPos numCols col (row - 1) Direction.Up)
+            | c -> failwith $"Unrecognised char: %c{c}"
+        | Direction.Left ->
+            match getAt numCols s row col with
+            | '-'
+            | '.' ->
+                if col > 0 then
+                    going.[going.Count - 1] <- storeDirectionAndPos numCols (col - 1) row dir
+                else
+                    going.RemoveAt (going.Count - 1)
+            | '\\' ->
+                if row > 0 then
+                    going.[going.Count - 1] <- storeDirectionAndPos numCols col (row - 1) Direction.Up
+                else
+                    going.RemoveAt (going.Count - 1)
+            | '/' ->
+                if row < numLines - 1 then
+                    going.[going.Count - 1] <- storeDirectionAndPos numCols col (row + 1) Direction.Down
+                else
+                    going.RemoveAt (going.Count - 1)
+            | '|' ->
+                going.RemoveAt (going.Count - 1)
+
+                if row < numLines - 1 then
+                    going.Add (storeDirectionAndPos numCols col (row + 1) Direction.Down)
+
+                if row > 0 then
+                    going.Add (storeDirectionAndPos numCols col (row - 1) Direction.Up)
+            | c -> failwith $"Unrecognised char: %c{c}"
+        | Direction.Up ->
+            match getAt numCols s row col with
+            | '|'
+            | '.' ->
+                if row > 0 then
+                    going.[going.Count - 1] <- storeDirectionAndPos numCols col (row - 1) dir
+                else
+                    going.RemoveAt (going.Count - 1)
+            | '/' ->
+                if col < numCols - 1 then
+                    going.[going.Count - 1] <- storeDirectionAndPos numCols (col + 1) row Direction.Right
+                else
+                    going.RemoveAt (going.Count - 1)
+            | '\\' ->
+                if col > 0 then
+                    going.[going.Count - 1] <- storeDirectionAndPos numCols (col - 1) row Direction.Left
+                else
+                    going.RemoveAt (going.Count - 1)
+            | '-' ->
+                going.RemoveAt (going.Count - 1)
+
+                if col < numCols - 1 then
+                    going.Add (storeDirectionAndPos numCols (col + 1) row Direction.Right)
+
+                if col > 0 then
+                    going.Add (storeDirectionAndPos numCols (col - 1) row Direction.Left)
+            | c -> failwith $"Unrecognised char: %c{c}"
+        | Direction.Down ->
+            match getAt numCols s row col with
+            | '|'
+            | '.' ->
+                if row < arr.Height - 1 then
+                    going.[going.Count - 1] <- storeDirectionAndPos numCols col (row + 1) dir
+                else
+                    going.RemoveAt (going.Count - 1)
+            | '\\' ->
+                if col < numCols - 1 then
+                    going.[going.Count - 1] <- storeDirectionAndPos numCols (col + 1) row Direction.Right
+                else
+                    going.RemoveAt (going.Count - 1)
+            | '/' ->
+                if col > 0 then
+                    going.[going.Count - 1] <- storeDirectionAndPos numCols (col - 1) row Direction.Left
+                else
+                    going.RemoveAt (going.Count - 1)
+            | '-' ->
+                going.RemoveAt (going.Count - 1)
+
+                if col < numCols - 1 then
+                    going.Add (storeDirectionAndPos numCols (col + 1) row Direction.Right)
+
+                if col > 0 then
+                    going.Add (storeDirectionAndPos numCols (col - 1) row Direction.Left)
+            | c -> failwith $"Unrecognised char: %c{c}"
+        | _ -> failwith "bad"
+
+    let part1 (s : string) =
+        let numLines = s.AsSpan().Count '\n'
+        let numCols = s.IndexOf '\n'
+        let buf = Array.zeroCreate (numLines * numCols)
+#if DEBUG
+        let arr : Arr2D<bool> =
+            {
+                Elements = buf
+                Width = numCols
+            }
+#else
+        use ptr = fixed buf
+
+        let arr : Arr2D<bool> =
+            {
+                Elements = ptr
+                Width = numCols
+                Length = buf.Length
+            }
+#endif
+        let going = ResizeArray ()
+
+        going.Add (storeDirectionAndPos numCols 0 0 Direction.Right)
+
+        let seen = Array.zeroCreate (int (maxEncoded numCols numLines) + 1)
+
+        while going.Count > 0 do
+            let nextUp = going.[going.Count - 1]
+
+            match seen.[int nextUp] with
+            | true -> going.RemoveAt (going.Count - 1)
+            | false ->
+                seen.[int nextUp] <- true
+                advance arr going s nextUp
+
+        buf.AsSpan().Count true
+
+    let part2 (s : string) =
+        let numLines = s.AsSpan().Count '\n'
+        let numCols = s.IndexOf '\n'
+        let buf = Array.zeroCreate (numLines * numCols)
+#if DEBUG
+        let arr : Arr2D<bool> =
+            {
+                Elements = buf
+                Width = numCols
+            }
+#else
+        use ptr = fixed buf
+
+        let arr : Arr2D<bool> =
+            {
+                Elements = ptr
+                Width = numCols
+                Length = buf.Length
+            }
+#endif
+        let going = ResizeArray ()
+        let seen = Array.zeroCreate (int (maxEncoded numCols numLines) + 1)
+        let mutable best = 0
+
+        for start = 0 to numCols - 1 do
+            going.Clear ()
+            Array.Clear seen
+            Array.Clear buf
+            going.Add (storeDirectionAndPos numCols start 0 Direction.Down)
+
+            while going.Count > 0 do
+                let nextUp = going.[going.Count - 1]
+
+                match seen.[int nextUp] with
+                | true -> going.RemoveAt (going.Count - 1)
+                | false ->
+                    seen.[int nextUp] <- true
+                    advance arr going s nextUp
+
+            let lit = buf.AsSpan().Count true
+            best <- max best lit
+
+            going.Clear ()
+            Array.Clear seen
+            Array.Clear buf
+            going.Add (storeDirectionAndPos numCols start (numLines - 1) Direction.Up)
+
+            while going.Count > 0 do
+                let nextUp = going.[going.Count - 1]
+
+                match seen.[int nextUp] with
+                | true -> going.RemoveAt (going.Count - 1)
+                | false ->
+                    seen.[int nextUp] <- true
+                    advance arr going s nextUp
+
+            let lit = buf.AsSpan().Count true
+            best <- max best lit
+
+        for start = 0 to numLines - 1 do
+            going.Clear ()
+            Array.Clear seen
+            Array.Clear buf
+            going.Add (storeDirectionAndPos numCols 0 start Direction.Right)
+
+            while going.Count > 0 do
+                let nextUp = going.[going.Count - 1]
+
+                match seen.[int nextUp] with
+                | true -> going.RemoveAt (going.Count - 1)
+                | false ->
+                    seen.[int nextUp] <- true
+                    advance arr going s nextUp
+
+            let lit = buf.AsSpan().Count true
+            best <- max best lit
+
+            going.Clear ()
+            Array.Clear seen
+            Array.Clear buf
+            going.Add (storeDirectionAndPos numCols (numCols - 1) start Direction.Left)
+
+            while going.Count > 0 do
+                let nextUp = going.[going.Count - 1]
+
+                match seen.[int nextUp] with
+                | true -> going.RemoveAt (going.Count - 1)
+                | false ->
+                    seen.[int nextUp] <- true
+                    advance arr going s nextUp
+
+            let lit = buf.AsSpan().Count true
+            best <- max best lit
+
+        best

AdventOfCode2023.FSharp/AdventOfCode2023.FSharp/Program.fs

@@ -300,6 +300,22 @@ module Program =
             Console.WriteLine (part2.ToString ())
             Console.Error.WriteLine ((1_000.0 * float sw.ElapsedTicks / float Stopwatch.Frequency).ToString () + "ms")
 
+        Console.WriteLine "=====Day 16====="
+
+        do
+            let input = Path.Combine (dir.FullName, "day16.txt") |> File.ReadAllText
+
+            sw.Restart ()
+            let part1 = Day16.part1 input
+            sw.Stop ()
+            Console.WriteLine (part1.ToString ())
+            Console.Error.WriteLine ((1_000.0 * float sw.ElapsedTicks / float Stopwatch.Frequency).ToString () + "ms")
+            sw.Restart ()
+            let part2 = Day16.part2 input
+            sw.Stop ()
+            Console.WriteLine (part2.ToString ())
+            Console.Error.WriteLine ((1_000.0 * float sw.ElapsedTicks / float Stopwatch.Frequency).ToString () + "ms")
+
         endToEnd.Stop ()
 
         Console.Error.WriteLine (

AdventOfCode2023.FSharp/Test/Test.fsproj

@@ -24,6 +24,7 @@
     <Compile Include="TestDay13.fs" />
     <Compile Include="TestDay14.fs" />
     <Compile Include="TestDay15.fs" />
+    <Compile Include="TestDay16.fs" />
     <EmbeddedResource Include="samples\day1.txt"/>
     <EmbeddedResource Include="samples\day1part1.txt"/>
     <EmbeddedResource Include="samples\day2.txt"/>
@@ -42,6 +43,7 @@
     <EmbeddedResource Include="samples\day13.txt" />
     <EmbeddedResource Include="samples\day14.txt" />
     <EmbeddedResource Include="samples\day15.txt" />
+    <EmbeddedResource Include="samples\day16.txt" />
   </ItemGroup>
 
   <ItemGroup>

AdventOfCode2023.FSharp/Test/TestDay16.fs

@@ -0,0 +1,44 @@
+namespace AdventOfCode2023.Test
+
+open AdventOfCode2023
+open NUnit.Framework
+open FsUnitTyped
+open System.IO
+
+[<TestFixture>]
+module TestDay16 =
+
+    [<Test>]
+    let sample = Assembly.getEmbeddedResource typeof<Dummy>.Assembly "day16.txt"
+
+    [<Test>]
+    let part1Sample () = sample |> Day16.part1 |> shouldEqual 46
+
+    [<Test>]
+    let part2Sample () = sample |> Day16.part2 |> shouldEqual 51
+
+    [<Test>]
+    let part1Actual () =
+        let s =
+            try
+                File.ReadAllText (Path.Combine (__SOURCE_DIRECTORY__, "../../inputs/day16.txt"))
+            with
+            | :? DirectoryNotFoundException
+            | :? FileNotFoundException ->
+                Assert.Inconclusive ()
+                failwith "unreachable"
+
+        Day16.part1 s |> shouldEqual 8112
+
+    [<Test>]
+    let part2Actual () =
+        let s =
+            try
+                File.ReadAllText (Path.Combine (__SOURCE_DIRECTORY__, "../../inputs/day16.txt"))
+            with
+            | :? DirectoryNotFoundException
+            | :? FileNotFoundException ->
+                Assert.Inconclusive ()
+                failwith "unreachable"
+
+        Day16.part2 s |> shouldEqual 8314

AdventOfCode2023.FSharp/Test/samples/day16.txt

@@ -0,0 +1,10 @@
+.|...\....
+|.-.\.....
+.....|-...
+........|.
+..........
+.........\
+..../.\\..
+.-.-/..|..
+.|....-|.\
+..//.|....