Day 4 (#5)

AdventOfCode2022.Test/AdventOfCode2022.Test.fsproj

@@ -10,9 +10,11 @@
         <Compile Include="Day1.fs" />
         <Compile Include="Day2.fs" />
         <Compile Include="Day3.fs" />
+        <Compile Include="Day4.fs" />
         <EmbeddedResource Include="Inputs/Day1.txt" />
         <EmbeddedResource Include="Inputs/Day2.txt" />
         <EmbeddedResource Include="Inputs\Day3.txt" />
+        <EmbeddedResource Include="Inputs\Day4.txt" />
     </ItemGroup>
 
     <ItemGroup>

AdventOfCode2022.Test/Day4.fs

@@ -0,0 +1,52 @@
+namespace AdventOfCode2022.Test
+
+open System
+open NUnit.Framework
+open FsUnitTyped
+open AdventOfCode2022
+
+[<TestFixture>]
+module TestDay4 =
+
+    [<Test>]
+    let ``Part 1, given`` () =
+        """2-4,6-8
+2-3,4-5
+5-7,7-9
+2-8,3-7
+6-6,4-6
+2-6,4-8"""
+        |> fun s -> s.Split System.Environment.NewLine
+        |> Day4.part1
+        |> shouldEqual 2
+
+    [<Test>]
+    let ``Part 1`` () =
+        let input = Assembly.readResource "Day4.txt"
+
+        input.Split '\n'
+        |> Seq.filter (not << String.IsNullOrWhiteSpace)
+        |> Day4.part1
+        |> shouldEqual 433
+
+
+    [<Test>]
+    let ``Part 2, given`` () =
+        """2-4,6-8
+2-3,4-5
+5-7,7-9
+2-8,3-7
+6-6,4-6
+2-6,4-8"""
+        |> fun s -> s.Split System.Environment.NewLine
+        |> Day4.part2
+        |> shouldEqual 4
+
+    [<Test>]
+    let ``Part 2`` () =
+        let input = Assembly.readResource "Day4.txt"
+
+        input.Split '\n'
+        |> Seq.filter (not << String.IsNullOrWhiteSpace)
+        |> Day4.part2
+        |> shouldEqual 852

AdventOfCode2022/AdventOfCode2022.fsproj

@@ -9,6 +9,7 @@
         <Compile Include="Day1.fs" />
         <Compile Include="Day2.fs" />
         <Compile Include="Day3.fs" />
+        <Compile Include="Day4.fs" />
         <Compile Include="Day3Efficient.fs" />
     </ItemGroup>
 

AdventOfCode2022/Day4.fs

@@ -0,0 +1,36 @@
+namespace AdventOfCode2022
+
+open System
+
+[<RequireQualifiedAccess>]
+module Day4 =
+
+    /// This only checks if the first arg fully contains the second arg.
+    let inline fullyContains (a, b) (c, d) : bool = a <= c && b >= d
+
+    let inline overlaps (a, b) (c, d) : bool = b >= c && a <= d
+
+    let parse (s : ReadOnlySpan<char>) : (int * int) * (int * int) =
+        let commaIndex = s.IndexOf ','
+        let firstElf = s.Slice (0, commaIndex)
+        let secondElf = s.Slice (commaIndex + 1)
+        let firstDashIndex = firstElf.IndexOf '-'
+        let firstElf1 = firstElf.Slice (0, firstDashIndex)
+        let firstElf2 = firstElf.Slice (firstDashIndex + 1)
+        let secondDashIndex = secondElf.IndexOf '-'
+        let secondElf1 = secondElf.Slice (0, secondDashIndex)
+        let secondElf2 = secondElf.Slice (secondDashIndex + 1)
+        (Int32.Parse firstElf1, Int32.Parse firstElf2), (Int32.Parse secondElf1, Int32.Parse secondElf2)
+
+    let part1 (lines : string seq) : int =
+        lines
+        |> Seq.map (fun s -> parse (s.AsSpan ()))
+        |> Seq.filter (fun (firstElf, secondElf) -> fullyContains firstElf secondElf || fullyContains secondElf firstElf
+        )
+        |> Seq.length
+
+    let part2 (lines : string seq) : int =
+        lines
+        |> Seq.map (fun s -> parse (s.AsSpan ()))
+        |> Seq.filter (fun (firstElf, secondElf) -> overlaps firstElf secondElf)
+        |> Seq.length