1. Queues, Deques, and Priority Queues Chapter 23 Carrano, Data Structures and Abstractions with Java, Second Edition, (c) 2007 Pearson Education, Inc. All rights reserved. 0-13-237045-X

2. Chapter Contents Specifications for the ADT Queue Using a Queue to Simulate a Waiting Line – The Classes WaitLine and Customer Using a Queue to Compute the capital Gain in a Sale of Stock – The Classes StockLedger and StockPurchase Java Class Library: the Interface Queue Specifications of the ADT Deque

3. Chapter Contents Using a Deque to Compute the Capital Gain in a Sale of Stock Specifications of the ADT Priority Queue Using a Priority Queue to Compute the Capital Gain in a Sale of Stock Specifications of the ADT Priority Queue Using a Priority Queue to Track Your Assignments

4. Specifications for the ADT Queue Queue organizes entries according to order of entry – Exhibits first-in, first-out behavior – Contrast to stack which is last-in, first-out All additions are at the back of the queue Front of queue has items added first

5. Specifications for the ADT Queue Fig. 23-1 Some everyday queues.

6. Specifications for the ADT Queue View interface for a queue of objects View interface Note methods – enqueue – dequeue – getFront – isEmpty – clear

7. Specifications for the ADT Queue Fig. 23-2 Queue of strings after (a) enqueue adds Jim; (b) Jess; (c) Jill; (d) Jane;

8. Specifications for the ADT Queue Fig. 23-2 Queue of strings after (e) enqueue adds Joe; (f) dequeue retrieves, removes Jim; (g) enqueue adds Jerry; (h) dequeue retrieves, removes Jess.

9. Using a Queue to Simulate a Waiting Line Fig. 23-3 A line, or queue of people.

10. Classes WaitLine and Customer Fig. 23-4 A CRC card for the class WaitLine.

11. Classes WaitLine and Customer Fig. 23-5 A diagram of the classes WaitLine and Customer.

12. Classes WaitLine and Customer Fig. 23-6 A simulated waiting line … continued →

13. Classes WaitLine and Customer Fig. 23-6 (ctd) A simulated waiting line.

14. The Class Waitline View source codesource code Note methods – Constructor – simulate – displayResults – reset

15. Using a Queue to Compute Capital Gain in a Sale of Stock Must sell stocks in same order they were purchased – Must use the difference in selling price and purchase price to calculate capital gain We use a queue to – Record investment transactions chronologically – Compute capital gain of the stock

16. Classes StockLedger and StockPurchase Fig. 23-7 A CRC card for the class StockLedger

17. Classes StockLedger and StockPurchase Fig. 23-8 A diagram of the class StockLedger and StockPurchase.

18. Classes StockLedger and StockPurchase View source code for class StockLedgersource code Note method – Constructor – buy – sell

19. Classes StockLedger and StockPurchase Fig. 23-9 A queue of (a) individual shares of stock; (b) grouped shares.

20. Java Class Library: The Interface Queue Similar to our QueueInterface – Specifies more methods Methods provided

21. Specifications of the ADT Deque A Double ended queue Has operations that – Add, remove, or retrieve entries – At both its front and back Combines and expands the operations of queue and stack

22. Specifications of the ADT Deque Fig. 23-10 An instance of a deque.

23. Specifications of the ADT Deque A Java interface

24. Specifications of the ADT Deque Fig. 23-11 A comparison of the operations that add, remove, and retrieve the entries of a stack s, queue q, and a deque d ; (a) add;

25. Specifications of the ADT Deque Fig. 23-11 A comparison of the operations that add, remove, and retrieve the entries of a stack s, queue q, and a deque d ; (b) remove;

26. Specifications of the ADT Deque Fig. 23-11 A comparison of the operations that add, remove, and retrieve the entries of a stack s, queue q, and a deque d ; (c) retrieve.

27. Using a Deque to Compute Capital Gain in Sale of Stock Revise the class StockPurchase – Represents purchase of n shares at d dollars per share – Constructor is changed – Accessor methods for new fields added Revise class StockLedger – Method ledger now an instance of a deque – Method buy now creates instance of StockPurchase, places it at back of deque – Method sell also altered Click to view new methods

28. Specifications of the ADT Priority Queue Organizes objects according to priorities – Contrast to regular queue in order of arrival Priority queue example – a hospital ER Priority can be specified by an integer – Must define whether high number is high priority or … – Low number (say 0) is high priority Other objects can specify priority – Object must have a compareTo method

29. Specifications of the ADT Priority Queue Note specification for ADT priority queuespecification Methods specified – add – remove – peek – getSize – clear

30. Using Priority Queue to Track Your Assignments Organize class or work assignments by due dates – Early due date, higher priority Figure 23-2 diagram of class Assignment

31. Using Priority Queue to Track Your Assignments Fig. 23-13 A diagram of the class AssignmentLog Note source code of classsource code