Day 4 (#2)

Reviewed-on: #2

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

@@ -11,6 +11,7 @@
         <Compile Include="Day1.fs" />
         <Compile Include="Day2.fs" />
         <Compile Include="Day3.fs" />
+        <Compile Include="Day4.fs" />
     </ItemGroup>
 
 </Project>

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

@@ -0,0 +1,97 @@
+namespace AdventOfCode2023
+
+open System
+open System.Collections.Generic
+
+[<RequireQualifiedAccess>]
+module Day4 =
+
+    let part1 (s : string) =
+        use lines = StringSplitEnumerator.make '\n' s
+        let mutable total = 0
+        let winningNumbers = HashSet ()
+
+        for line in lines do
+            if not (line.IsWhiteSpace ()) then
+                let mutable accumulatingWinning = true
+                winningNumbers.Clear ()
+                use mutable split = StringSplitEnumerator.make' ' ' line
+                StringSplitEnumerator.chomp "Card" &split
+
+                while split.Current.IsEmpty || split.Current.[split.Current.Length - 1] <> ':' do
+                    split.MoveNext () |> ignore
+
+                split.MoveNext () |> ignore
+
+                while accumulatingWinning do
+                    while split.Current.IsEmpty do
+                        split.MoveNext () |> ignore
+
+                    if split.Current.[0] = '|' then
+                        accumulatingWinning <- false
+                    else
+                        winningNumbers.Add (Int32.Parse split.Current) |> ignore
+                        split.MoveNext () |> ignore
+
+                let mutable answer = 0
+
+                while split.MoveNext () do
+                    if not split.Current.IsEmpty then
+                        let n = Int32.Parse split.Current
+
+                        if winningNumbers.Contains n then
+                            answer <- answer + 1
+
+                if answer > 0 then
+                    total <- total + (1 <<< (answer - 1))
+
+        total
+
+
+
+    let part2 (s : string) =
+        use lines = StringSplitEnumerator.make '\n' s
+        let mutable total = 0
+        let winningNumbers = HashSet ()
+        let winners = ResizeArray ()
+
+        for line in lines do
+            if not (line.IsWhiteSpace ()) then
+                let mutable accumulatingWinning = true
+                winningNumbers.Clear ()
+                use mutable split = StringSplitEnumerator.make' ' ' line
+                StringSplitEnumerator.chomp "Card" &split
+
+                while split.Current.IsEmpty || split.Current.[split.Current.Length - 1] <> ':' do
+                    split.MoveNext () |> ignore
+
+                split.MoveNext () |> ignore
+
+                while accumulatingWinning do
+                    while split.Current.IsEmpty do
+                        split.MoveNext () |> ignore
+
+                    if split.Current.[0] = '|' then
+                        accumulatingWinning <- false
+                    else
+                        winningNumbers.Add (Int32.Parse split.Current) |> ignore
+                        split.MoveNext () |> ignore
+
+                let mutable answer = 0
+
+                while split.MoveNext () do
+                    if not split.Current.IsEmpty then
+                        let n = Int32.Parse split.Current
+
+                        if winningNumbers.Contains n then
+                            answer <- answer + 1
+
+                winners.Add answer
+
+        let ans = Array.create winners.Count 1
+
+        for i = 0 to winners.Count - 1 do
+            for j = i + 1 to winners.[i] + i do
+                ans.[j] <- ans.[j] + ans.[i]
+
+        ans |> Array.sum