initial commit

79.fs

@@ -0,0 +1,33 @@
+module _79
+
+open System.IO
+
+let findPasscode =
+    let logins = 
+        File.ReadAllLines(@"79_keylog.txt") 
+    let preceeds = 
+        logins 
+        |> Seq.collect (fun login -> seq { yield (login.[0], login.[1]); yield (login.[1], login.[2]) })
+        |> Seq.distinct
+
+    let collectTuple (a,b) =
+        seq { yield a; yield b }
+
+    // topographical sort kinda
+    let rec orderGraph g =
+        seq {
+            if Seq.length g = 1 then 
+                yield (collectTuple (Seq.nth 0 g)) |> Seq.toList
+            else
+                let allNodes = g |> Seq.collect collectTuple |> Seq.distinct |> Set.ofSeq
+                let sndNodes = g |> Seq.map snd |> Seq.distinct |> Set.ofSeq
+                let noPreceedingNodes = allNodes - sndNodes
+                for n in noPreceedingNodes do
+                    let gMinusN = g |> Seq.filter (fun gi -> not(fst gi = n))
+                    for s in orderGraph gMinusN do
+                        yield n :: s
+        }
+    
+    preceeds
+    |> orderGraph
+    |> Seq.toArray