From: Grégory Burri <gregory.burri@matisa.ch>
Date: Wed, 5 Dec 2018 12:30:57 +0000 (+0100)
Subject: Day 5.
X-Git-Url: https://git.euphorik.ch/?a=commitdiff_plain;h=8940d4c6238e40041417e59cea4b87f1fc50aa0b;p=advent_of_code_2018.git

Day 5.
---

diff --git a/Day05.fs b/Day05.fs
index f2a0f10..accb3f9 100644
--- a/Day05.fs
+++ b/Day05.fs
@@ -1,7 +1,21 @@
 module AdventOfCode2018.Day05
 
 open System
-open System.Collections.Generic
 
-let parseInput (str : string) : string =
-    ""
+let diffMajMin = int 'A' - int 'a'
+
+let reduce (polymer : string) : string =
+    Seq.foldBack (
+        fun a result ->
+            match result with
+            | b :: rest when int a - int b |> abs = diffMajMin -> rest
+            | _ -> a :: result
+    ) polymer [ ]
+    |> Array.ofList
+    |> String.Concat
+
+let findShortestPolymer (polymer : string) : string =
+    polymer.ToLower()
+    |> Seq.distinct
+    |> Seq.map (fun unit -> polymer.Replace(string unit, "", StringComparison.InvariantCultureIgnoreCase) |> reduce)
+    |> Seq.minBy String.length
diff --git a/Program.fs b/Program.fs
index 418610f..2ff2dd3 100644
--- a/Program.fs
+++ b/Program.fs
@@ -22,8 +22,8 @@ let day04 () =
     sprintf "part1 = %A, part2 = %A" (sleepestGuardId * sleepestTime) (sleepestGuardIdSameTime * sleepestTimeSameTime)
 
 let day05 () =
-    let foo = File.ReadAllText "Data/day05.input" |> Day05.parseInput
-    sprintf "part1 = , part2 = "
+    let reduced = (File.ReadAllText "Data/day05.input").Trim () |> Day05.reduce
+    sprintf "part1 = %A, part2 = %A" reduced.Length (Day05.findShortestPolymer reduced).Length
 
 let days : Map<int, unit -> string> =
     [
diff --git a/Tests/Day05 tests.fs b/Tests/Day05 tests.fs
index aa0794c..6c47069 100644
--- a/Tests/Day05 tests.fs	
+++ b/Tests/Day05 tests.fs	
@@ -12,9 +12,11 @@ type ``Day05 tests`` (output : ITestOutputHelper) =
 
     [<Fact>]
     let ``(Part1) From web page`` () =
-        ()
+        let input = "dabAcCaCBAcCcaDA"
+        Day05.reduce input =! "dabCBAcaDA"
 
     [<Fact>]
     let ``(Part2) From web page`` () =
-        ()
+        let input = "dabAcCaCBAcCcaDA"
+        Day05.findShortestPolymer input =! "daDA"