2 files changed, 73 insertions, 0 deletions
diff --git a/aoc-2022-dotnet/Day20/Day20.fsproj b/aoc-2022-dotnet/Day20/Day20.fsproj
new file mode 100644
index 0000000..795d59c
--- /dev/null
+++ b/aoc-2022-dotnet/Day20/Day20.fsproj
@@ -0,0 +1,26 @@
+<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>
+    <PackageReference Include="FSharpPlus" Version="1.3.2" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Common\Common.fsproj" />
+  </ItemGroup>
+
+</Project>
diff --git a/aoc-2022-dotnet/Day20/Program.fs b/aoc-2022-dotnet/Day20/Program.fs
new file mode 100644
index 0000000..9453a8d
--- /dev/null
+++ b/aoc-2022-dotnet/Day20/Program.fs
@@ -0,0 +1,47 @@
+module Day20
+
+open System.IO
+open FSharpPlus.Math.Generic
+open Common
+
+let mix listWithIds =
+    let cycle = List.length listWithIds - 1
+
+    let move xs idToMove =
+        let oldIndex = List.findIndex (fst >> (=) idToMove) xs
+        let element = xs[oldIndex]
+        let newIndex = int <| remE (int64 oldIndex + snd element) cycle
+
+        xs
+        |> List.removeAt oldIndex
+        |> List.insertAt newIndex element
+
+    seq { 0..cycle } |> Seq.fold move listWithIds
+
+let nthAfterZero n xs =
+    xs
+    |> List.item (remE (List.findIndex (snd >> (=) 0L) xs + n) (List.length xs))
+    |> snd
+
+let groveCoords multiplier rounds input =
+    let mixed =
+        input
+        |> Seq.map (int64 >> (*) multiplier)
+        |> Seq.indexed
+        |> List.ofSeq
+        |> Util.composition rounds mix
+
+    nthAfterZero 1000 mixed
+    + nthAfterZero 2000 mixed
+    + nthAfterZero 3000 mixed
+
+let solution1 = groveCoords 1 1
+let solution2 = groveCoords 811589153 10
+
+let test = File.ReadLines("test.txt")
+assert (solution1 test = 3)
+assert (solution2 test = 1623178306)
+
+let input = File.ReadLines("input.txt")
+printfn "%d" <| solution1 input
+printfn "%d" <| solution2 input