Cleaner

AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/Day6.fs

@@ -7,26 +7,33 @@ module Day6 =
 
     let parse (s : string) =
         use mutable lines = StringSplitEnumerator.make '\n' s
+
         let times =
             lines.MoveNext () |> ignore
             use mutable line = StringSplitEnumerator.make' ' ' lines.Current
             StringSplitEnumerator.chomp "Time:" &line
             line.MoveNext () |> ignore
             let times = ResizeArray ()
+
             while line.MoveNext () do
                 if not line.Current.IsEmpty then
                     times.Add (UInt64.Parse line.Current)
+
             times
+
         let distance =
             lines.MoveNext () |> ignore
             use mutable line = StringSplitEnumerator.make' ' ' lines.Current
             StringSplitEnumerator.chomp "Distance:" &line
             line.MoveNext () |> ignore
             let distance = ResizeArray ()
+
             while line.MoveNext () do
                 if not line.Current.IsEmpty then
                     distance.Add (UInt64.Parse line.Current)
+
             distance
+
         times, distance
 
     let furthest (distance : uint64) (toBeat : uint64) =
@@ -50,37 +57,30 @@ module Day6 =
     let part1 (s : string) =
         let times, distance = parse s
         let mutable answer = 1uL
+
         for i = 0 to times.Count - 1 do
             let time = times.[i]
             let distance = distance.[i]
             let winners = furthest time distance
             answer <- answer * winners
+
+        answer
+
+    let concat (digits : ResizeArray<uint64>) : uint64 =
+        let mutable answer = 0uL
+
+        for digit in digits do
+            let mutable power = 10uL
+
+            while digit >= power do
+                power <- power * 10uL
+
+            answer <- answer * power + digit
+
         answer
 
     let part2 (s : string) =
         let times, distance = parse s
-        let mutable concatTime = 0uL
-        for time in times do
-            // four digits will do
-            if time < 10uL then
-                concatTime <- concatTime * 10uL + time
-            elif time < 100uL then
-                concatTime <- concatTime * 100uL + time
-            elif time < 1000uL then
-                concatTime <- concatTime * 1000uL + time
-            else
-                concatTime <- concatTime * 10000uL + time
-
-        let mutable concatDist = 0uL
-        for dist in distance do
-            // four digits will do
-            if dist < 10uL then
-                concatDist <- concatDist * 10uL + dist
-            elif dist < 100uL then
-                concatDist <- concatDist * 100uL + dist
-            elif dist < 1000uL then
-                concatDist <- concatDist * 1000uL + dist
-            else
-                concatDist <- concatDist * 10000uL + dist
-
+        let concatTime = concat times
+        let concatDist = concat distance
         furthest concatTime concatDist