Create activity-participants.sql

Author: kamyu104

MySQL/activity-participants.sql

@@ -0,0 +1,18 @@
+# Time:  O(n) 
+# Space: O(n) 
+
+SELECT activity 
+FROM   friends 
+GROUP  BY activity 
+HAVING Count(1) NOT IN (SELECT Max(counts) 
+                        FROM   (SELECT Count(1) AS counts 
+                                FROM   friends 
+                                GROUP  BY activity 
+                                ORDER  BY NULL) a 
+                        UNION ALL 
+                        SELECT Min(counts) 
+                        FROM   (SELECT Count(1) AS counts 
+                                FROM   friends 
+                                GROUP  BY activity 
+                                ORDER  BY NULL) b) 
+ORDER  BY NULL;