Iniital commit

.gitignore

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ConsoleApp2.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "ConsoleApp2", "ConsoleApp2\ConsoleApp2.fsproj", "{D18D6A10-3AAB-4F2A-8CE6-C0D598A8E144}"
+EndProject
+Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "Solve.Test", "Solve.Test\Solve.Test.fsproj", "{A4D67E0D-4DE2-4F6F-A443-6BE3B735C173}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{D18D6A10-3AAB-4F2A-8CE6-C0D598A8E144}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D18D6A10-3AAB-4F2A-8CE6-C0D598A8E144}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D18D6A10-3AAB-4F2A-8CE6-C0D598A8E144}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D18D6A10-3AAB-4F2A-8CE6-C0D598A8E144}.Release|Any CPU.Build.0 = Release|Any CPU
+		{A4D67E0D-4DE2-4F6F-A443-6BE3B735C173}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{A4D67E0D-4DE2-4F6F-A443-6BE3B735C173}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{A4D67E0D-4DE2-4F6F-A443-6BE3B735C173}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{A4D67E0D-4DE2-4F6F-A443-6BE3B735C173}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+EndGlobal

ConsoleApp2/BondSet.fs

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+namespace Solve
+
+type BondSet =
+    private
+    | BondSet of ((int * int) * (int * int)) Set
+
+[<RequireQualifiedAccess>]
+module BondSet =
+    let sort a b = if a < b then (a, b) else (b, a)
+
+    let addIfOk ((sourceX, sourceY) as source) ((destX, destY) as dest) (BondSet bonds) : BondSet option =
+        let distance = abs (sourceX - destX) + abs (sourceY - destY)
+        if distance = 2 then
+            // Check the other
+            if sourceX < destX && sourceY < destY then
+                if bonds.Contains (sort (sourceX + 1, sourceY) (sourceX, sourceY + 1)) then
+                    None
+                else
+                    bonds
+                    |> Set.add (sort source dest)
+                    |> BondSet
+                    |> Some
+            elif sourceX > destX && sourceY > destY then
+                if bonds.Contains (sort (sourceX - 1, sourceY) (sourceX, sourceY - 1)) then
+                    None
+                else
+                    bonds
+                    |> Set.add (sort source dest)
+                    |> BondSet
+                    |> Some
+            elif sourceX < destX then
+                if bonds.Contains (sort (sourceX, sourceY - 1) (sourceX + 1, sourceY)) then
+                    None
+                else
+                    bonds
+                    |> Set.add (sort source dest)
+                    |> BondSet
+                    |> Some
+            else
+                if bonds.Contains (sort (sourceX - 1, sourceY) (sourceX, sourceY + 1)) then
+                    None
+                else
+                    bonds
+                    |> Set.add (sort source dest)
+                    |> BondSet
+                    |> Some
+
+        else
+            if distance <> 1 then failwith "bad assumption"
+            bonds
+            |> Set.add (sort source dest)
+            |> BondSet
+            |> Some
+
+    let empty = BondSet Set.empty
+
+    let directionList (BondSet s) =
+        let rec go (acc : _ list) (start : int * int) (s : Set<_>) =
+            if s.IsEmpty then List.rev (start :: acc) else
+            let next, toRem =
+                s
+                |> Seq.choose (fun (p1, p2) ->
+                    if p1 = start then Some (p2, (p1, p2))
+                    elif p2 = start then Some (p1, (p1, p2))
+                    else None
+                )
+                |> Seq.exactlyOne
+            go (start :: acc) next (Set.remove toRem s)
+
+        go [] (0, 0) s
+
+

ConsoleApp2/ConsoleApp2.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>net7.0</TargetFramework>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <Compile Include="Seq.fs" />
+        <Compile Include="BondSet.fs" />
+        <Compile Include="Program.fs" />
+    </ItemGroup>
+
+</Project>

ConsoleApp2/Program.fs

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+namespace Solve
+
+module Program =
+
+    let words =
+        [
+            "LEAD"
+            "BEAD"
+            "BEAR"
+            "BEAT"
+            "BOAT"
+            "BOOT"
+            "BOLT"
+            "COLT"
+            "CULT"
+            "CURT"
+            "CART"
+            "CARD"
+            "CARE"
+            "DARE"
+            "DANE"
+            "DONE"
+            "DONG"
+            "DING"
+            "MING"
+            "MINX"
+            "MIND"
+            "MEND"
+            "MELD"
+            "MEAD"
+        ]
+
+    let instructions =
+        words @ [ List.head words ]
+        |> List.pairwise
+        |> List.map (fun (start, next) ->
+            let instruction =
+                [1..4]
+                |> List.filter (fun i ->
+                    start.[i - 1] <> next.[i - 1]
+                )
+                |> List.exactlyOne
+            start, instruction
+        )
+
+    let restrict (board : Map<int * int, string>) =
+        if Seq.range (board.Keys |> Seq.map snd) > 5 then false
+        elif Seq.range (board.Keys |> Seq.map fst) > 7 then false
+        else true
+
+    let rec go
+        (currX : int)
+        (currY : int)
+        (bonds : BondSet)
+        (board : Map<int * int, string>)
+        (instructions : (string * int) list)
+        : _ list
+        =
+        //if not (restrict board) then [] else
+        match instructions with
+        | [] -> [board, BondSet.directionList bonds]
+        | (word, i) :: rest ->
+            // Place this word.
+            let newBoard =
+                board
+                |> Map.add (currX, currY) word
+
+            match i with
+            | 1 ->
+                // horizontal, i.e. change X
+                [
+                    match Map.tryFind (currX + 1, currY) newBoard with
+                    | None ->
+                        match bonds |> BondSet.addIfOk (currX + 1, currY) (currX, currY) with
+                        | None -> ()
+                        | Some bonds ->
+                            yield! go (currX + 1) currY bonds newBoard rest
+                    | Some _ -> ()
+                    match Map.tryFind (currX - 1, currY) newBoard with
+                    | None ->
+                        match bonds |> BondSet.addIfOk (currX - 1, currY) (currX, currY) with
+                        | None -> ()
+                        | Some bonds ->
+                            yield! go (currX - 1) currY bonds newBoard rest
+                    | Some _ -> ()
+                ]
+            | 2 ->
+                // vertical, i.e. change Y
+                [
+                    match Map.tryFind (currX, currY + 1) newBoard with
+                    | None ->
+                        match bonds |> BondSet.addIfOk (currX, currY + 1) (currX, currY) with
+                        | None -> ()
+                        | Some bonds ->
+                            yield! go currX (currY + 1) bonds newBoard rest
+                    | Some _ -> ()
+                    match Map.tryFind (currX, currY - 1) newBoard with
+                    | None ->
+                        match bonds |> BondSet.addIfOk (currX, currY - 1) (currX, currY) with
+                        | None -> ()
+                        | Some bonds ->
+                            yield! go currX (currY - 1) bonds newBoard rest
+                    | Some _ -> ()
+                ]
+            | 3 ->
+                // Bottom left to top right
+                [
+                    match Map.tryFind (currX + 1, currY + 1) newBoard with
+                    | None ->
+                        match bonds |> BondSet.addIfOk (currX + 1, currY + 1) (currX, currY) with
+                        | None -> ()
+                        | Some bonds ->
+                            yield! go (currX + 1) (currY + 1) bonds newBoard rest
+                    | Some _ -> ()
+                    match Map.tryFind (currX - 1, currY - 1) newBoard with
+                    | None ->
+                        match bonds |> BondSet.addIfOk (currX - 1, currY - 1) (currX, currY) with
+                        | None -> ()
+                        | Some bonds ->
+                            yield! go (currX - 1) (currY - 1) bonds newBoard rest
+                    | Some _ -> ()
+                ]
+            | 4 ->
+                // Top left to bottom right
+                [
+                    match Map.tryFind (currX - 1, currY + 1) newBoard with
+                    | None ->
+                        match bonds |> BondSet.addIfOk (currX - 1, currY + 1) (currX, currY) with
+                        | None -> ()
+                        | Some bonds ->
+                            yield! go (currX - 1) (currY + 1) bonds newBoard rest
+                    | Some _ -> ()
+                    match Map.tryFind (currX + 1, currY - 1) newBoard with
+                    | None ->
+                        match bonds |> BondSet.addIfOk (currX + 1, currY - 1) (currX, currY) with
+                        | None -> ()
+                        | Some bonds ->
+                            yield! go (currX + 1) (currY - 1) bonds newBoard rest
+                    | Some _ -> ()
+                ]
+            | _ -> failwith "bad direction"
+
+    let print ((x, y), s) =
+        printfn "%i, %i: %s" x y s
+
+    [<EntryPoint>]
+    let main _ =
+        let after =
+            instructions
+            |> go 0 0 BondSet.empty Map.empty
+            |> List.map (fun (examplePlacement, exampleBonds) ->
+                let munged =
+                    exampleBonds
+                    |> List.choose (fun (srcX, srcY) ->
+                        match examplePlacement.TryFind (srcX, srcY) with
+                        | Some w ->
+                            Some ((srcX, srcY), w)
+                        | None ->
+                            None
+                    )
+                munged
+            )
+        printfn "Before filtering, %i options" after.Length
+        after.[7000] |> List.iter print
+        let filtered =
+            after
+            |> List.filter (fun positions ->
+                let (endX, endY) = fst (List.last positions)
+                endY = 0 && (abs endX = 1)
+            )
+        printfn "%i total options" filtered.Length
+        0

ConsoleApp2/Seq.fs

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+namespace Solve
+
+[<RequireQualifiedAccess>]
+module Seq =
+
+    let range (s : int seq) : int =
+        use e = s.GetEnumerator ()
+        if not (e.MoveNext ()) then 0 else
+
+        let mutable min = e.Current
+        let mutable max = e.Current
+        while e.MoveNext () do
+            if e.Current < min then min <- e.Current
+            if e.Current > max then max <- e.Current
+        max - min
+

Solve.Test/Program.fs

@@ -0,0 +1,4 @@
+module Program =
+
+    [<EntryPoint>]
+    let main _ = 0

Solve.Test/Solve.Test.fsproj

@@ -0,0 +1,29 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net7.0</TargetFramework>
+
+        <IsPackable>false</IsPackable>
+        <GenerateProgramFile>false</GenerateProgramFile>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <Compile Include="UnitTest1.fs" />
+        <Compile Include="Program.fs" />
+    </ItemGroup>
+
+    <ItemGroup>
+        <PackageReference Include="FsCheck" Version="2.16.5" />
+        <PackageReference Include="FsUnit" Version="5.2.0" />
+        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.2" />
+        <PackageReference Include="NUnit" Version="3.13.3" />
+        <PackageReference Include="NUnit3TestAdapter" Version="4.2.1" />
+        <PackageReference Include="NUnit.Analyzers" Version="3.3.0" />
+        <PackageReference Include="coverlet.collector" Version="3.1.2" />
+    </ItemGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\ConsoleApp2\ConsoleApp2.fsproj" />
+    </ItemGroup>
+
+</Project>

Solve.Test/UnitTest1.fs

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+namespace Solve.Test
+
+open FsUnitTyped
+open NUnit.Framework
+open Solve
+open FsCheck
+
+[<TestFixture>]
+module TestSeq =
+
+    [<Test>]
+    let ``Seq.range works`` () : unit =
+        Seq.range Seq.empty |> shouldEqual 0
+
+        let prop (i : int) (s : int list) =
+            let s = i :: s
+            Seq.range s
+            |> (=) (Seq.max s - Seq.min s)
+
+        prop
+        |> Check.QuickThrowOnFailure