A shorter day 5 solution.

diff --git a/Day05.fs b/Day05.fs
index accb3f9..a752d91 100644 (file)
--- a/Day05.fs
+++ b/Day05.fs
@@ -2,20 +2,19 @@ module AdventOfCode2018.Day05
 \r
 open System\r
 \r
-let diffMajMin = int 'A' - int 'a'\r
+let diffMajMin = int 'a' - int 'A'\r
 \r
-let reduce (polymer : string) : string =\r
-    Seq.foldBack (\r
+let reduce (polymer : char list) : char list =\r
+    List.foldBack (\r
         fun a result ->\r
             match result with\r
             | b :: rest when int a - int b |> abs = diffMajMin -> rest\r
             | _ -> a :: result\r
     ) polymer [ ]\r
-    |> Array.ofList\r
-    |> String.Concat\r
 \r
-let findShortestPolymer (polymer : string) : string =\r
-    polymer.ToLower()\r
-    |> Seq.distinct\r
-    |> Seq.map (fun unit -> polymer.Replace(string unit, "", StringComparison.InvariantCultureIgnoreCase) |> reduce)\r
-    |> Seq.minBy String.length\r
+let findShortestPolymer (polymer : char list) : char list =\r
+    polymer\r
+    |> List.map Char.ToLower\r
+    |> List.distinct\r
+    |> List.map (fun unit -> polymer |> List.filter (fun c -> Char.ToLower c <> unit) |> reduce)\r
+    |> List.minBy List.length\r

diff --git a/Program.fs b/Program.fs
index 2ff2dd3..fb433b7 100644 (file)
--- a/Program.fs
+++ b/Program.fs
@@ -22,7 +22,7 @@ let day04 () =
     sprintf "part1 = %A, part2 = %A" (sleepestGuardId * sleepestTime) (sleepestGuardIdSameTime * sleepestTimeSameTime)\r
 \r
 let day05 () =\r
-    let reduced = (File.ReadAllText "Data/day05.input").Trim () |> Day05.reduce\r
+    let reduced = (File.ReadAllText "Data/day05.input").Trim () |> List.ofSeq |> Day05.reduce\r
     sprintf "part1 = %A, part2 = %A" reduced.Length (Day05.findShortestPolymer reduced).Length\r
 \r
 let days : Map<int, unit -> string> =\r

diff --git a/Tests/Day05 tests.fs b/Tests/Day05 tests.fs
index 6c47069..560db29 100644 (file)
--- a/Tests/Day05 tests.fs
+++ b/Tests/Day05 tests.fs
@@ -12,11 +12,11 @@ type ``Day05 tests`` (output : ITestOutputHelper) =
 \r
     [<Fact>]\r
     let ``(Part1) From web page`` () =\r
-        let input = "dabAcCaCBAcCcaDA"\r
-        Day05.reduce input =! "dabCBAcaDA"\r
+        let input = List.ofSeq "dabAcCaCBAcCcaDA"\r
+        Day05.reduce input =! List.ofSeq "dabCBAcaDA"\r
 \r
     [<Fact>]\r
     let ``(Part2) From web page`` () =\r
-        let input = "dabAcCaCBAcCcaDA"\r
-        Day05.findShortestPolymer input =! "daDA"\r
+        let input = List.ofSeq "dabAcCaCBAcCcaDA"\r
+        Day05.findShortestPolymer input =! List.ofSeq "daDA"\r
 \r