From 19cef44652bad540b9046dc2a05e50061e010ab8 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Gr=C3=A9gory=20Burri?= <gregory.burri@matisa.ch>
Date: Fri, 7 Dec 2018 14:02:29 +0100
Subject: [PATCH] Day 7, part 1.

---
 AdventOfCode2018.fsproj |  4 ++++
 Day07.fs                | 26 ++++++++++++++++++++++++++
 Program.fs              |  5 +++++
 Tests/Day07 tests.fs    | 29 +++++++++++++++++++++++++++++
 Tests/Tests.fsproj      |  1 +
 5 files changed, 65 insertions(+)
 create mode 100644 Day07.fs
 create mode 100644 Tests/Day07 tests.fs

diff --git a/AdventOfCode2018.fsproj b/AdventOfCode2018.fsproj
index 7026dc3..e78a65c 100644
--- a/AdventOfCode2018.fsproj
+++ b/AdventOfCode2018.fsproj
@@ -4,6 +4,7 @@
     <TargetFramework>netcoreapp2.1</TargetFramework>
   </PropertyGroup>
   <ItemGroup>
+    <Compile Include="Day07.fs" />
     <Compile Include="Day06.fs" />
     <Compile Include="Day05.fs" />
     <Compile Include="Day04.fs" />
@@ -11,6 +12,9 @@
     <Compile Include="Day02.fs" />
     <Compile Include="Day01.fs" />
     <Compile Include="Program.fs" />
+    <Content Include="Data/day07.input">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
     <Content Include="Data/day06.input">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
diff --git a/Day07.fs b/Day07.fs
new file mode 100644
index 0000000..9274501
--- /dev/null
+++ b/Day07.fs
@@ -0,0 +1,26 @@
+module AdventOfCode2018.Day07
+
+open System
+
+type Constraint = char * char
+
+let parseInput (str : string) : Constraint array =
+    str.Split ([| '\r'; '\n'; |], StringSplitOptions.RemoveEmptyEntries)
+    |> Array.map (
+        fun line ->
+            let trimmedLine = line.Trim  ()
+            trimmedLine.[5], trimmedLine.[36]
+    )
+
+let order (constraints : Constraint array) : char array =
+    let constraints = constraints |> Array.sortBy fst
+
+    let rec loop (constraints : Constraint array) : char list =
+        match constraints with
+        | [| (a, b) |] -> [ a; b ]
+        | _ ->
+            let next = constraints |> Array.pick (fun (a, _) -> if constraints |> Array.forall (fun (_, b) -> a <> b) then Some a else None)
+            let rest = constraints |> Array.filter (fst >> ((<>) next))
+            next :: (loop rest)
+
+    loop constraints |> Array.ofList
\ No newline at end of file
diff --git a/Program.fs b/Program.fs
index fcb5fc1..ac4a5d3 100644
--- a/Program.fs
+++ b/Program.fs
@@ -29,6 +29,10 @@ let day06 () =
     let coords = File.ReadAllText "Data/day06.input" |> Day06.parseInput
     sprintf "part1 = %A, part2 = %A" (Day06.getLargestArea coords) (Day06.getAreaWithTotalDistanceLessThan 10000 coords)
 
+let day07 () =
+    let constraints = File.ReadAllText "Data/day07.input" |> Day07.parseInput
+    sprintf "part1 = %A, part2 =" (Day07.order constraints |> String.Concat)
+
 let days : Map<int, unit -> string> =
     [
         1, day01
@@ -37,6 +41,7 @@ let days : Map<int, unit -> string> =
         4, day04
         5, day05
         6, day06
+        7, day07
     ] |> Map.ofList
 
 let doDay (n : int) =
diff --git a/Tests/Day07 tests.fs b/Tests/Day07 tests.fs
new file mode 100644
index 0000000..6a96601
--- /dev/null
+++ b/Tests/Day07 tests.fs	
@@ -0,0 +1,29 @@
+namespace AdventOfCode2018.Tests
+
+open System
+
+open Xunit
+open Xunit.Abstractions
+open Swensen.Unquote
+
+open AdventOfCode2018
+
+type ``Day07 tests`` (output : ITestOutputHelper) =
+    let input =
+        """Step C must be finished before step A can begin.
+           Step C must be finished before step F can begin.
+           Step A must be finished before step B can begin.
+           Step A must be finished before step D can begin.
+           Step B must be finished before step E can begin.
+           Step D must be finished before step E can begin.
+           Step F must be finished before step E can begin."""
+
+    [<Fact>]
+    let ``(Part1) From web page`` () =
+        let constrains = Day07.parseInput input
+        Day07.order constrains |> String.Concat =! "CABDFE"
+
+    [<Fact>]
+    let ``(Part2) From web page`` () =
+        ()
+
diff --git a/Tests/Tests.fsproj b/Tests/Tests.fsproj
index 0042788..b905858 100644
--- a/Tests/Tests.fsproj
+++ b/Tests/Tests.fsproj
@@ -6,6 +6,7 @@
     <ProjectReference Include="..\AdventOfCode2018.fsproj" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Day07 tests.fs" />
     <Compile Include="Day06 tests.fs" />
     <Compile Include="Day05 tests.fs" />
     <Compile Include="Day04 tests.fs" />
-- 
2.45.2