Create find-the-missing-ids.sql

Author: kamyu104

MySQL/find-the-missing-ids.sql

@@ -0,0 +1,18 @@
+# Time:  O(n^2)
+# Space: O(n)
+
+WITH RECURSIVE Seq AS
+  (SELECT 1 AS continued_id
+   UNION ALL SELECT continued_id + 1
+   FROM Seq
+   WHERE continued_id <
+       (SELECT MAX(customer_id)
+        FROM Customers) )
+
+SELECT continued_id AS ids
+FROM Seq s
+WHERE NOT EXISTS
+    (SELECT customer_id
+     FROM Customers c
+     WHERE c.customer_id = s.continued_id);
+