Day 5 (#4)

Co-authored-by: Smaug123 <patrick+github@patrickstevens.co.uk>
Reviewed-on: #4

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

@@ -12,6 +12,7 @@
         <Compile Include="Day2.fs" />
         <Compile Include="Day3.fs" />
         <Compile Include="Day4.fs" />
+        <Compile Include="Day5.fs" />
     </ItemGroup>
 
 </Project>

AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/Day4.fs

@@ -1,15 +1,22 @@
 namespace AdventOfCode2023
 
 open System
-open System.Collections.Generic
+open System.Globalization
 
 [<RequireQualifiedAccess>]
 module Day4 =
 
+    let inline parseByte (chars : ReadOnlySpan<char>) : byte =
+        Byte.Parse (chars, NumberStyles.None, NumberFormatInfo.InvariantInfo)
+    //let mutable answer = 0uy
+    //for c in chars do
+    //    answer <- answer * 10uy + (byte c - 48uy)
+    //answer
+
     let part1 (s : string) =
         use lines = StringSplitEnumerator.make '\n' s
         let mutable total = 0
-        let winningNumbers = HashSet ()
+        let winningNumbers = ResizeArray<byte> ()
 
         for line in lines do
             if not (line.IsWhiteSpace ()) then
@@ -30,14 +37,14 @@ module Day4 =
                     if split.Current.[0] = '|' then
                         accumulatingWinning <- false
                     else
-                        winningNumbers.Add (Int32.Parse split.Current) |> ignore
+                        winningNumbers.Add (parseByte split.Current)
                         split.MoveNext () |> ignore
 
                 let mutable answer = 0
 
                 while split.MoveNext () do
                     if not split.Current.IsEmpty then
-                        let n = Int32.Parse split.Current
+                        let n = parseByte split.Current
 
                         if winningNumbers.Contains n then
                             answer <- answer + 1
@@ -51,9 +58,8 @@ module Day4 =
 
     let part2 (s : string) =
         use lines = StringSplitEnumerator.make '\n' s
-        let mutable total = 0
-        let winningNumbers = HashSet ()
-        let winners = ResizeArray ()
+        let winningNumbers = ResizeArray<byte> ()
+        let winners = ResizeArray<int> ()
 
         for line in lines do
             if not (line.IsWhiteSpace ()) then
@@ -74,14 +80,14 @@ module Day4 =
                     if split.Current.[0] = '|' then
                         accumulatingWinning <- false
                     else
-                        winningNumbers.Add (Int32.Parse split.Current) |> ignore
+                        winningNumbers.Add (parseByte split.Current)
                         split.MoveNext () |> ignore
 
                 let mutable answer = 0
 
                 while split.MoveNext () do
                     if not split.Current.IsEmpty then
-                        let n = Int32.Parse split.Current
+                        let n = parseByte split.Current
 
                         if winningNumbers.Contains n then
                             answer <- answer + 1

AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/Day5.fs

@@ -0,0 +1,191 @@
+namespace AdventOfCode2023
+
+open System
+
+[<Struct>]
+type Range =
+    {
+        SourceStart : uint32
+        DestStart : uint32
+        Len : uint32
+    }
+
+[<RequireQualifiedAccess>]
+module Day5 =
+
+    let parse (s : string) =
+        use mutable lines = StringSplitEnumerator.make '\n' s
+        lines.MoveNext () |> ignore
+
+        let seeds =
+            use mutable line1 = StringSplitEnumerator.make' ' ' lines.Current
+            StringSplitEnumerator.chomp "seeds:" &line1
+            let result = ResizeArray ()
+
+            while line1.MoveNext () do
+                result.Add (UInt32.Parse line1.Current)
+
+            result.ToArray ()
+
+        lines.MoveNext () |> ignore
+
+        let mappings = ResizeArray ()
+
+        let mutable currentMapping = null
+
+        for line in lines do
+            if line.IsEmpty then
+                if not (isNull currentMapping) then
+                    mappings.Add currentMapping
+                    currentMapping <- null
+            else if isNull currentMapping then
+                currentMapping <- ResizeArray ()
+            else
+                use mutable line = StringSplitEnumerator.make' ' ' line
+                let destStart = StringSplitEnumerator.consumeU32 &line
+                let sourceStart = StringSplitEnumerator.consumeU32 &line
+                let rangeLen = StringSplitEnumerator.consumeU32 &line
+
+                {
+                    SourceStart = sourceStart
+                    DestStart = destStart
+                    Len = rangeLen
+                }
+                |> currentMapping.Add
+
+        seeds, mappings
+
+    let part1 (s : string) =
+        let seeds, mappings = parse s
+
+        let mutable best = UInt32.MaxValue
+
+        for seed in seeds do
+            let mutable remapped = seed
+
+            for map in mappings do
+                let mutable hasRemappedThisLayer = false
+
+                for interval in map do
+                    if not hasRemappedThisLayer then
+                        if
+                            interval.SourceStart <= remapped
+                            && remapped - interval.SourceStart < interval.Len
+                        then
+                            hasRemappedThisLayer <- true
+                            remapped <- remapped + (interval.DestStart - interval.SourceStart)
+
+            if remapped < best then
+                best <- remapped
+
+        best
+
+    // The input ranges are inclusive at both ends.
+    // Returns any range we didn't map.
+    let private split
+        (resultStarts : ResizeArray<uint32>)
+        (resultEnds : ResizeArray<uint32>)
+        start
+        finish
+        (rangeFromLayer : Range)
+        : (uint32 * uint32 * (uint32 * uint32) voption) voption
+        =
+        let low = rangeFromLayer.SourceStart
+        let high = rangeFromLayer.SourceStart + rangeFromLayer.Len - 1ul
+
+        if low <= start then
+            if finish <= high then
+                // low ... start .. finish .. high
+                // so the entire input range gets mapped down
+                resultStarts.Add (start + rangeFromLayer.DestStart - rangeFromLayer.SourceStart)
+                resultEnds.Add (finish + rangeFromLayer.DestStart - rangeFromLayer.SourceStart)
+
+                ValueNone
+            elif start <= high then
+                // low .. start .. high .. finish
+                // so start .. high gets mapped down
+                // and high + 1 .. finish stays where it is.
+                // high < finish is already guaranteed by previous if block.
+                resultStarts.Add (start + rangeFromLayer.DestStart - rangeFromLayer.SourceStart)
+                resultEnds.Add (high + rangeFromLayer.DestStart - rangeFromLayer.SourceStart)
+
+                ValueSome (high + 1ul, finish, ValueNone)
+            else
+                ValueSome (start, finish, ValueNone)
+        else if high <= finish then
+            // start .. low .. high .. finish
+            // so start .. low - 1 stays where it is
+            // low .. high gets mapped down
+            // and high + 1 .. finish stays where it is
+            resultStarts.Add (low + rangeFromLayer.DestStart - rangeFromLayer.SourceStart)
+            resultEnds.Add (high + rangeFromLayer.DestStart - rangeFromLayer.SourceStart)
+
+            ValueSome (start, low - 1ul, ValueSome (high + 1ul, finish))
+        elif low < finish then
+            // start .. low .. finish .. high
+            // so start .. low - 1 stays where it is
+            // and low .. finish gets mapped down
+            resultStarts.Add (low + rangeFromLayer.DestStart - rangeFromLayer.SourceStart)
+            resultEnds.Add (finish + rangeFromLayer.DestStart - rangeFromLayer.SourceStart)
+
+            ValueSome (start, low - 1ul, ValueNone)
+        else
+            ValueSome (start, finish, ValueNone)
+
+    let part2 (s : string) : uint32 =
+        let seeds, mappings = parse s
+
+        let mutable intervalStarts = ResizeArray ()
+        let mutable intervalEnds = ResizeArray ()
+
+        for i = 0 to (seeds.Length - 1) / 2 do
+            intervalStarts.Add seeds.[2 * i]
+            intervalEnds.Add (seeds.[2 * i + 1] + seeds.[2 * i] - 1ul)
+
+        let mutable nextIntervalStarts = ResizeArray ()
+        let mutable nextIntervalEnds = ResizeArray ()
+
+        for mapLayer in mappings do
+            let mutable i = 0
+
+            while i < intervalStarts.Count do
+                // split interval according to every map
+                let mutable allMoved = false
+                let mutable currentRange = 0
+
+                while not allMoved && currentRange < mapLayer.Count do
+                    let range = mapLayer.[currentRange]
+                    // range is e.g. 50 98 2, i.e. "98-99 goes to 50-51"
+                    match split nextIntervalStarts nextIntervalEnds intervalStarts.[i] intervalEnds.[i] range with
+                    | ValueNone -> allMoved <- true
+                    | ValueSome (start, finish, v) ->
+                        intervalStarts.[i] <- start
+                        intervalEnds.[i] <- finish
+
+                        match v with
+                        | ValueNone -> ()
+                        | ValueSome (start, finish) ->
+                            intervalStarts.Add start
+                            intervalEnds.Add finish
+
+                    currentRange <- currentRange + 1
+
+                if not allMoved then
+                    nextIntervalStarts.Add intervalStarts.[i]
+                    nextIntervalEnds.Add intervalEnds.[i]
+
+                i <- i + 1
+
+            let oldIntervals = intervalStarts
+            oldIntervals.Clear ()
+            intervalStarts <- nextIntervalStarts
+            nextIntervalStarts <- oldIntervals
+
+            let oldIntervals = intervalEnds
+            oldIntervals.Clear ()
+            intervalEnds <- nextIntervalEnds
+            nextIntervalEnds <- oldIntervals
+
+
+        // SIMD go brrr
+        System.Linq.Enumerable.Min intervalStarts

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

@@ -95,3 +95,15 @@ module StringSplitEnumerator =
             failwith "expected an int, got nothing"
 
         Int32.Parse e.Current
+
+    let consumeU32 (e : byref<StringSplitEnumerator>) : uint32 =
+        if not (e.MoveNext ()) then
+            failwith "expected an int, got nothing"
+
+        UInt32.Parse e.Current
+
+    let consumeU64 (e : byref<StringSplitEnumerator>) : uint64 =
+        if not (e.MoveNext ()) then
+            failwith "expected an int, got nothing"
+
+        UInt64.Parse e.Current