fix binary tree inserts

lab03/kvtree.ml

@@ -17,6 +17,8 @@ let rec kvtree_insert ~cmp k v t =
     Node (k', v', kvtree_insert ~cmp k v l, r)
   | Node (k', v', l, r) when cmp k k' > 0 ->
     Node (k', v', l, kvtree_insert ~cmp k v r)
+  | Node (k', _, l, r) when cmp k k' = 0 ->
+    Node (k, v, l, r)
   | _ -> t;;
 
 (**/**)2

lab05/kvtree/kvtree.ml

@@ -45,6 +45,8 @@ module Make(Ord: OrderedType) = struct
       N (k', v', insert k v l, r)
     | N (k', v', l, r) when Ord.compare k k' > 0 ->
       N (k', v', l, insert k v r)
+    | N (k', _, l, r) when Ord.compare k k' = 0 ->
+      N (k, v, l, r)
     | _ -> t;;
 
   (** [find_opt k t] takes a key [k] and a kvtree [t] and returns