Stacks and Queues & Inheritance

1. Stacks and Queues & Inheritance 2014 Spring CS32 Discussion JungseockJoo

2. Stacks and Queues • Dynamic 1-dimensional data structures • Insertion & deletion of elements (push & pop) • Take place only in either side of list

3. Stacks and Queues • Stack : Last-in-first-out • Queue : First-in-first-out

4. Stacks and Queues • Q: Can we just use a linked-list with restrictions on insertions and deletions?

5. Stacks and Queues • Q: Can we just use a linked-list with restrictions on insertions and deletions? • A: That is a stack (or queue)

6. Stacks and Queues • Usually – not always, • You start with an empty stack (or queue) • Insertion/deletion is incremental. • By the end of your program, they become empty again because you have all the items processed.

7. Implementation • By a linked list • void push( const ItemType& new_item ); • Place the new_item at the “end” of current list • “end” – top in stacks, back in queues • void pop(); • Delete the top item (stack) or the front item (queue) • Destruct the item • Then adjust the pointers of items and # of items accordingly

8. Implementation • By a linked list • ItemType& top(); • Only in stack, returns the top item • ItemType& front(); • Only in queue, returns the front item

9. Implementation • Q: I need to access items in the middle • A: Then you don’t use stacks or queues

10. Stack vs. Queue • When do you use what? • Depends on the particular order of items to process. • E.g., Depth-first-search vs. Breadth-first-search

11. Inheritance

12. Inheritance • To organize related classes (or objects) in a hierarchy.

13. Inheritance • Why? • To reduce code redundancy • By sharing the same functions/variables among a group of classes. • Sharing is directed, so inherited • From base-class to derived-class • Polymorphism

14. Inheritance • A “BaseballPlayer” is a “Person” • An “Employee” is a “Person” • A “Supervisor” is an “Employee” • A “Supervisor” is a “Person”

15. Inheritance Base-class • A “BaseballPlayer” is a “Person” • An “Employee” is a “Person” • A “Supervisor” is an “Employee” • A “Supervisor” is a “Person” Derived-class

16. Inheritance • A “BaseballPlayer” is a “Person” • An “Employee” is a “Person” • A “Supervisor” is an “Employee” • A “Supervisor” is a “Person” Base-class Derived-class

17. Inheritance Base-class • A base-class defines functions/variables to share with its derived classes • Person.age() • Person.gender() Derived-class

18. Inheritance Base-class • A derived-class defines its own specific functions/variables • BaseballPlayer.team() • Employee.company() • Supervisor.subordinates() • It can also modify inherited functions, if needed. Derived-class

19. Example

20. Example

21. Automatic Conversion

22. Automatic Conversion • So we can do..

23. Inheritance of Members • All public members are inherited. • Intget_age(); • Intm_age; • They can be used in derived classes. • Not constructor, destructor, assignment operator..

24. Function Overriding • When you want to replace an existing function:

26. Virtual Function • Overriding functions: • Multiple definitions with the same signature • We need to choose a specific one to run

27. Virtual Function • Non-virtual functions: • According to the type of pointer or reference

28. Virtual Function • Virtual functions • According to “actual” type

29. Virtual Function

30. Pure Virtual Function