add lecture 08

lectures/08/rbtree.ml

@@ -0,0 +1,23 @@
+type color = R | B
+
+type 'a rbtree = L | N of color * 'a rbtree * 'a * 'a rbtree
+
+let balance = function
+  | B, N (R, N (R, a, x, b), y, c), z, d
+  | B, N (R, a, x, N (R, b, y, c)), z, d
+  | B, a, x, N (R, N (R, b, y, c), z, d)
+  | B, a, x, N (R, b, y, N (R, c, z, d)) ->
+    N (R, N (B, a, x, b), y, N (B, c, z, d))
+  | c, l, x, r ->
+    N (c, l, x, r)
+
+let insert x t =
+  let rec ins = function
+    | L -> N (R, L, x, L)
+    | N (c, l, y, r) when x < y ->
+      balance (c, ins l, x, r)
+    | N (c, l, y, r) when x > y ->
+      balance (c, l, x, ins r)
+    | _ -> t
+  in
+  ins t