Add IntMapHelper, locate wall cutting bug

src/IntMapHelp.hs

@@ -0,0 +1,21 @@
+module IntMapHelp
+    ( module Data.IntMap.Strict
+    , newKey
+    , insertNewKey
+    , insertWithNewKeys
+    )
+    where
+--import Data.List hiding (foldr,insert)
+import Data.IntMap.Strict
+{- | Find a key value one higher than any key in the map, or zero if the map is
+ - empty -}
+newKey :: IntMap a -> Int
+newKey = maybe 0 ((+ 1) . fst) . lookupMax
+{- | Insert an element with some new key. -}
+insertNewKey :: a -> IntMap a -> IntMap a
+insertNewKey x m = case lookupMax m of
+    Nothing     -> singleton 0 x
+    Just (k,_)  -> insert (k+1) x m
+{- | Insert a list of values with new keys -}
+insertWithNewKeys :: [a] -> IntMap a -> IntMap a
+insertWithNewKeys xs m = union m $ fromList $ zip [newKey m..] xs