Day 1

diff --git a/Day01.fs b/Day01.fs
index ca6f6b2..5659b61 100644 (file)
--- a/Day01.fs
+++ b/Day01.fs
@@ -1,5 +1,23 @@
 module AdventOfCode2018.Day01\r
 \r
-let readDigit d = int d - int '0'\r
+open System\r
 \r
-let parseInput (str : string) : string = str\r
+\r
+let parseInput (str : string) : int[] =\r
+    str.Split ([| "\r\n"; "\r"; "\n" |], StringSplitOptions.RemoveEmptyEntries) |> Array.map int\r
+\r
+let finalFrequency : seq<int> -> int =\r
+    Seq.sum\r
+\r
+let firstDuplicate (changes : seq<int>) : int =\r
+    let repeatedChanges = seq { while true do yield! changes }\r
+    Seq.scan (\r
+        fun (_, sum, frequencies) change ->\r
+            let sum' = sum + change\r
+            if Set.contains sum' frequencies then\r
+                (true, sum', frequencies)\r
+            else\r
+                (false, sum', Set.add sum' frequencies)\r
+\r
+    ) (false, 0, Set.empty) repeatedChanges\r
+    |> Seq.pick (fun (duplicate, sum, _) -> if duplicate then Some sum else None)\r

diff --git a/Program.fs b/Program.fs
index 1f93628..b3c7fb0 100644 (file)
--- a/Program.fs
+++ b/Program.fs
@@ -4,8 +4,8 @@ open System
 open System.IO\r
 \r
 let day01 () =\r
-    let input = File.ReadAllText "Data/day01.input" |> Day01.parseInput\r
-    input\r
+    let changes = File.ReadAllText "Data/day01.input" |> Day01.parseInput\r
+    sprintf "part1 = %A, part2 = %A" (Day01.finalFrequency changes) (Day01.firstDuplicate changes)\r
 \r
 let days : (unit -> string) array =\r
     [|\r