Finish day 24

2 files changed, 129 insertions, 0 deletions

diff --git a/aoc-2022-dotnet/Day24/Day24.fsproj b/aoc-2022-dotnet/Day24/Day24.fsproj
new file mode 100644
index 0000000..b9a3919
--- /dev/null
+++ b/aoc-2022-dotnet/Day24/Day24.fsproj
@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Content Include="test.txt">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </Content>
+    <Content Include="input.txt">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </Content>
+    <Compile Include="Program.fs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Common\Common.fsproj" />
+  </ItemGroup>
+
+</Project>
diff --git a/aoc-2022-dotnet/Day24/Program.fs b/aoc-2022-dotnet/Day24/Program.fs
new file mode 100644
index 0000000..0446c06
--- /dev/null
+++ b/aoc-2022-dotnet/Day24/Program.fs
@@ -0,0 +1,107 @@
+module Day24
+
+open System.IO
+open FSharpPlus
+open Common
+
+type Valley =
+    { MaxX: int
+      MaxY: int
+      ExpeditionSuperposition: Set<Vec2>
+      Walls: Set<Vec2>
+      Blizzards: Map<Vec2, Set<Vec2>> }
+
+    static member private empty =
+        { MaxX = 0
+          MaxY = 0
+          ExpeditionSuperposition = Set.empty
+          Walls = Set.empty
+          Blizzards =
+            Vec2.directions4
+            |> Set.map (fun d -> d, Set.empty)
+            |> Map.ofSeq }
+
+    static member private withExpeditionAt target valley =
+        { valley with ExpeditionSuperposition = Set.singleton <| target valley }
+
+    static member private hasReached target valley =
+        Set.contains (target valley) valley.ExpeditionSuperposition
+
+    static member startOf({ MaxY = maxY }) = Vec2(1, maxY)
+    static member endOf({ MaxX = maxX }) = Vec2(maxX - 1, 0)
+
+    static member parse input =
+        input
+        |> Seq.rev
+        |> array2D
+        |> Array2D.mapi (fun r c char -> Vec2(c, r), char)
+        |> Seq.cast
+        |> Seq.fold
+            (fun valley (pos, char) ->
+                match char with
+                | '.' -> valley
+                | '#' ->
+                    { valley with
+                        Walls = valley.Walls.Add(pos)
+                        MaxX = max valley.MaxX pos.x
+                        MaxY = max valley.MaxY pos.y }
+                | '^'
+                | '>'
+                | 'v'
+                | '<' ->
+                    { valley with Blizzards = valley.Blizzards.Change(Vec2.dirFromChar char, Option.map <| Set.add pos) }
+                | c -> failwithf "Invalid valley character: %c" c)
+            Valley.empty
+        |> Valley.withExpeditionAt Valley.startOf
+
+    member private valley.moveBlizzard offset pos =
+        pos + offset
+        |> Vec2.mapX (Util.wrapInRangeInc 1 (valley.MaxX - 1))
+        |> Vec2.mapY (Util.wrapInRangeInc 1 (valley.MaxY - 1))
+
+    static member private step valley =
+        let valley =
+            { valley with Blizzards = Map.map (fun dir -> Set.map <| valley.moveBlizzard dir) valley.Blizzards }
+
+        { valley with
+            ExpeditionSuperposition =
+                valley.ExpeditionSuperposition
+                |> Seq.collect Vec2.neighbours5
+                |> Seq.filter (fun pos ->
+                    pos.y >= 0
+                    && pos.y <= valley.MaxY
+                    && Util.notIn valley.Walls pos
+                    && Seq.forall (not << Set.contains pos) valley.Blizzards.Values)
+                |> Set }
+
+    static member moveTo target valley =
+        Some(valley, 0)
+        |> Seq.unfold (
+            Option.map
+            <| fun (v, m) ->
+                (v, m),
+                match Valley.hasReached target v with
+                | true -> None
+                | false -> Some(Valley.step v, m + 1)
+        )
+        |> Seq.last
+        |> mapItem1 (Valley.withExpeditionAt target)
+
+let solution1 = Valley.parse >> Valley.moveTo Valley.endOf >> snd
+
+let solution2 input =
+    let valley = Valley.parse input
+
+    let (valley, minutes1) = Valley.moveTo Valley.endOf valley
+    let (valley, minutes2) = Valley.moveTo Valley.startOf valley
+    let (_, minutes3) = Valley.moveTo Valley.endOf valley
+
+    minutes1 + minutes2 + minutes3
+
+let test = File.ReadLines("test.txt")
+assert (solution1 test = 18)
+assert (solution2 test = 54)
+
+let input = File.ReadLines("input.txt")
+printfn "%d" <| solution1 input
+printfn "%d" <| solution2 input