Day 9

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

@@ -10,6 +10,7 @@
     <Compile Include="ResizeArray.fs"/>
     <Compile Include="EfficientString.fs"/>
     <Compile Include="Arithmetic.fs"/>
+    <Compile Include="Rational.fs"/>
     <Compile Include="Day1.fs"/>
     <Compile Include="Day2.fs"/>
     <Compile Include="Day3.fs"/>
@@ -18,6 +19,7 @@
     <Compile Include="Day6.fs"/>
     <Compile Include="Day7.fs"/>
     <Compile Include="Day8.fs"/>
+    <Compile Include="Day9.fs"/>
   </ItemGroup>
 
 </Project>

AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/Day9.fs

@@ -0,0 +1,55 @@
+namespace AdventOfCode2023
+
+open System
+
+[<RequireQualifiedAccess>]
+module Day9 =
+
+    let extrapolate (isStart : bool) (arr : ResizeArray<int64>) =
+        let mutable answer = 0L
+        let pos = if isStart then -1L else int64 arr.Count
+
+        for i = 0 to arr.Count - 1 do
+            let mutable product = Rational.ofInt arr.[i]
+
+            for j = 0 to arr.Count - 1 do
+                if j <> i then
+                    product <- product * Rational.make (pos - int64 j) (int64 i - int64 j)
+
+            answer <- answer + Rational.assertIntegral product
+
+        answer
+
+    let part1 (s : string) =
+        use s = StringSplitEnumerator.make '\n' s
+        let mutable answer = 0L
+        let arr = ResizeArray ()
+
+        for line in s do
+            arr.Clear ()
+            use line = StringSplitEnumerator.make' ' ' line
+
+            for number in line do
+                let number = Int64.Parse number
+                arr.Add number
+
+            answer <- answer + extrapolate false arr
+
+        answer
+
+    let part2 (s : string) =
+        use s = StringSplitEnumerator.make '\n' s
+        let mutable answer = 0L
+        let arr = ResizeArray ()
+
+        for line in s do
+            arr.Clear ()
+            use line = StringSplitEnumerator.make' ' ' line
+
+            for number in line do
+                let number = Int64.Parse number
+                arr.Add number
+
+            answer <- answer + extrapolate true arr
+
+        answer

AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/EfficientString.fs

@@ -1,7 +1,6 @@
 namespace AdventOfCode2023
 
 open System
-open System.Globalization
 open System.Runtime.CompilerServices
 
 type EfficientString = System.ReadOnlySpan<char>

AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/Rational.fs

@@ -0,0 +1,82 @@
+namespace AdventOfCode2023
+
+[<Struct>]
+type Rational<'a
+    when 'a : (static member (+) : 'a * 'a -> 'a)
+    and 'a : (static member (*) : 'a * 'a -> 'a)
+    and 'a : (static member (/) : 'a * 'a -> 'a)
+    and 'a : (static member (-) : 'a * 'a -> 'a)
+    and 'a : (static member Zero : 'a)
+    and 'a : (static member One : 'a)
+    and 'a : comparison> =
+    {
+        Numerator : 'a
+        Denominator : 'a
+    }
+
+    static member inline (+) (a : Rational<'a>, b : Rational<'a>) =
+        let numerator = a.Numerator * b.Denominator + b.Numerator * a.Denominator
+        let denominator = a.Denominator * b.Denominator
+        let hcf = (Arithmetic.euclideanAlgorithm numerator denominator).Hcf
+
+        {
+            Numerator = numerator / hcf
+            Denominator = denominator / hcf
+        }
+
+    static member inline (*) (a : Rational<'a>, b : Rational<'a>) =
+        let numerator = a.Numerator * b.Numerator
+        let denominator = a.Denominator * b.Denominator
+        let hcf = (Arithmetic.euclideanAlgorithm numerator denominator).Hcf
+
+        {
+            Numerator = numerator / hcf
+            Denominator = denominator / hcf
+        }
+
+[<RequireQualifiedAccess>]
+module Rational =
+    let inline ofInt< ^a
+        when 'a : (static member (+) : 'a * 'a -> 'a)
+        and 'a : (static member (*) : 'a * 'a -> 'a)
+        and 'a : (static member (/) : 'a * 'a -> 'a)
+        and 'a : (static member (-) : 'a * 'a -> 'a)
+        and 'a : (static member Zero : 'a)
+        and 'a : (static member One : 'a)
+        and 'a : comparison>
+        (a : 'a)
+        =
+        {
+            Numerator = a
+            Denominator = LanguagePrimitives.GenericOne
+        }
+
+    let inline make< ^a
+        when 'a : (static member (+) : 'a * 'a -> 'a)
+        and 'a : (static member (*) : 'a * 'a -> 'a)
+        and 'a : (static member (/) : 'a * 'a -> 'a)
+        and 'a : (static member (-) : 'a * 'a -> 'a)
+        and 'a : (static member Zero : 'a)
+        and 'a : (static member One : 'a)
+        and 'a : comparison>
+        (numerator : 'a)
+        (denominator : 'a)
+        =
+        let hcf = (Arithmetic.euclideanAlgorithm numerator denominator).Hcf
+
+        {
+            Numerator = numerator / hcf
+            Denominator = denominator / hcf
+        }
+
+    let inline assertIntegral< ^a
+        when 'a : (static member (+) : 'a * 'a -> 'a)
+        and 'a : (static member (*) : 'a * 'a -> 'a)
+        and 'a : (static member (/) : 'a * 'a -> 'a)
+        and 'a : (static member (-) : 'a * 'a -> 'a)
+        and 'a : (static member Zero : 'a)
+        and 'a : (static member One : 'a)
+        and 'a : comparison>
+        (r : Rational<'a>)
+        =
+        r.Numerator

AdventOfCode2023.FSharp/AdventOfCode2023.FSharp/Program.fs

@@ -179,6 +179,22 @@ module Program =
             Console.WriteLine (part2.ToString ())
             Console.Error.WriteLine ((1_000.0 * float sw.ElapsedTicks / float Stopwatch.Frequency).ToString () + "ms")
 
+        Console.WriteLine "=====Day 9====="
+
+        do
+            let input = Path.Combine (dir.FullName, "day9.txt") |> File.ReadAllText
+
+            sw.Restart ()
+            let part1 = Day9.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 = Day9.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

@@ -17,6 +17,7 @@
     <Compile Include="TestDay6.fs"/>
     <Compile Include="TestDay7.fs"/>
     <Compile Include="TestDay8.fs"/>
+    <Compile Include="TestDay9.fs"/>
     <EmbeddedResource Include="samples\day1.txt"/>
     <EmbeddedResource Include="samples\day1part1.txt"/>
     <EmbeddedResource Include="samples\day2.txt"/>
@@ -27,6 +28,7 @@
     <EmbeddedResource Include="samples\day7.txt"/>
     <EmbeddedResource Include="samples\day8part1.txt"/>
     <EmbeddedResource Include="samples\day8.txt"/>
+    <EmbeddedResource Include="samples\day9.txt"/>
   </ItemGroup>
 
   <ItemGroup>

AdventOfCode2023.FSharp/Test/TestDay5.fs

@@ -1,6 +1,5 @@
 namespace AdventOfCode2023.Test
 
-open System
 open AdventOfCode2023
 open NUnit.Framework
 open FsUnitTyped

AdventOfCode2023.FSharp/Test/TestDay6.fs

@@ -1,6 +1,5 @@
 namespace AdventOfCode2023.Test
 
-open System
 open AdventOfCode2023
 open NUnit.Framework
 open FsUnitTyped

AdventOfCode2023.FSharp/Test/TestDay7.fs

@@ -1,6 +1,5 @@
 namespace AdventOfCode2023.Test
 
-open System
 open AdventOfCode2023
 open NUnit.Framework
 open FsUnitTyped

AdventOfCode2023.FSharp/Test/TestDay9.fs

@@ -0,0 +1,47 @@
+namespace AdventOfCode2023.Test
+
+open AdventOfCode2023
+open NUnit.Framework
+open FsUnitTyped
+open System.IO
+
+[<TestFixture>]
+module TestDay9 =
+
+    let sample = Assembly.getEmbeddedResource typeof<Dummy>.Assembly "day9.txt"
+
+    [<Test>]
+    let part1Sample () =
+        sample |> Day9.part1 |> shouldEqual 114L
+
+    [<Test>]
+    let part2Sample () =
+        Assembly.getEmbeddedResource typeof<Dummy>.Assembly "day9.txt"
+        |> Day9.part2
+        |> shouldEqual 2L
+
+    [<Test>]
+    let part1Actual () =
+        let s =
+            try
+                File.ReadAllText (Path.Combine (__SOURCE_DIRECTORY__, "../../inputs/day9.txt"))
+            with
+            | :? DirectoryNotFoundException
+            | :? FileNotFoundException ->
+                Assert.Inconclusive ()
+                failwith "unreachable"
+
+        Day9.part1 s |> shouldEqual 1898776583L
+
+    [<Test>]
+    let part2Actual () =
+        let s =
+            try
+                File.ReadAllText (Path.Combine (__SOURCE_DIRECTORY__, "../../inputs/day9.txt"))
+            with
+            | :? DirectoryNotFoundException
+            | :? FileNotFoundException ->
+                Assert.Inconclusive ()
+                failwith "unreachable"
+
+        Day9.part2 s |> shouldEqual 1100L

AdventOfCode2023.FSharp/Test/samples/day9.txt

@@ -0,0 +1,3 @@
+0 3 6 9 12 15
+1 3 6 10 15 21
+10 13 16 21 30 45