The Ghost Deletion Queue

In a task processing system, tasks are added to a queue. However, a task can be cancelled (deleted) at any time before it is processed. If a task ID is deleted, all instances of that ID currently in the queue must be ignored when they eventually reach the head of the queue. Input Format: Commands: 'ADD ID', 'DELETE ID', 'PROCESS'. Output Format: For 'PROCESS', print the ID of the task being handled. If no valid tasks remain, print 'EMPTY'. Example: Input: ADD 101 ADD 102 DELETE 101 PROCESS PROCESS Output: 102 EMPTY