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

@@ -42,9 +42,11 @@ module Make(Ord: OrderedType) = struct
     match t with
     | L -> N (k, v, L, L)
     | N (k', v', l, r) when Ord.compare k k' < 0 ->
-      N (k', v', insert  k v l, r)
+      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', 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