1 files changed, 15 insertions, 0 deletions
diff --git a/Puzzle16.hs b/Puzzle16.hs
new file mode 100644
index 0000000..a15f802
--- /dev/null
+++ b/Puzzle16.hs
@@ -0,0 +1,15 @@
+import Data.List (elemIndex)
+import Data.Maybe (fromJust)
+
+spin n xs = let (ys, zs) = splitAt n xs in zs ++ ys
+
+exchange m n xs 
+  | n > m = ys ++ [y] ++ zs ++ [x] ++ ws
+  | n == m = xs
+  | otherwise = exchange n m xs
+      where (ys, x:xs') = splitAt m xs
+            (zs, y:ws)  = splitAt (n - m - 1) xs'
+
+partner x y xs = exchange m n xs
+  where m = fromJust $ elemIndex x xs
+        n = fromJust $ elemIndex y xs