initial commit

59.fs

@@ -0,0 +1,56 @@
+module _59
+
+open System
+open System.IO
+
+let cypher = 
+    let encrypted = 
+        File.ReadAllLines(@"59_cipher1.txt") 
+        |> Array.collect (fun line -> line.Split(',') |> Array.map uint16)
+    
+    let decrypt f message key =
+        let repeatedKey = seq { while true do yield! key }
+        Seq.map2 f message repeatedKey
+
+    let decryptXor = decrypt (^^^)
+
+    let decriptMessage = decryptXor encrypted
+
+    let de = encrypted |> Seq.distinct |> Seq.toArray
+    
+    let filteri f s =
+        seq {
+            for i in 0..((s |> Seq.length) - 1) do
+                let si = Seq.nth i s
+                if f i si then yield si
+        }
+
+    let validKeys encryptedSymbols = 
+        let lowercase = [97us..122us] |> List.toArray
+        let validSymbols = [32us..122us] |> List.toArray
+        
+        let isValidChar i =
+            Array.exists ((=) i) validSymbols
+
+        [0..2]
+        |> List.map (fun offset ->
+            lowercase
+            |> Seq.filter (fun lc ->
+                encryptedSymbols 
+                |> filteri (fun i e -> i % 3 = offset)
+                |> Seq.forall (fun e -> (e ^^^ lc) |> isValidChar))
+            )
+
+    let messageToText message =
+        message
+        |> Seq.map (char >> string)
+        |> Seq.fold (fun acc e -> acc + e) ""
+
+    validKeys encrypted
+    |> common.slottedPermutations
+    |> Seq.map (fun p -> (p, (decriptMessage >> messageToText) p))
+    |> Seq.find (fun p -> (snd p).Contains(" the "))
+    |> (fst >> decriptMessage)
+    |> Seq.map (int)
+    |> Seq.sum
+