Initial data commit

Task/Run-length-encoding/Haskell/run-length-encoding-3.hs

@@ -0,0 +1,25 @@
+import Data.Char (isDigit)
+import Data.List (span)
+
+encode :: String -> String
+encode [] = []
+encode (x : xs) =
+  let (run, rest) = span (x ==) xs
+   in x : (show . succ . length) run <> encode rest
+
+decode :: String -> String
+decode [] = []
+decode (x : xs) =
+  let (ds, rest) = span isDigit xs
+      n = read ds :: Int
+   in replicate n x <> decode rest
+
+main :: IO ()
+main =
+  putStrLn encoded
+    >> putStrLn decoded
+    >> print (src == decoded)
+  where
+    src = "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW"
+    encoded = encode src
+    decoded = decode encoded