Lecture 6 Data Structures

1. Lecture 6 Data Structures

2. Stack top

3. 2 4 6 8 9 top 2 4 6 8 9 x

4. 2 4 6 8 9 top 2 4 6 8 9 x

5. Queue head tail 1 3 6 2 5

6. 1 2 3 tail 1 2 3 x

7. x 1 2 3 head 1 2 3

8. Priority Queue • A priority queue is a data structure for maintaining a set of elements, each with an associated value, called a key. • A max-priority queue supports the following operations: Insert(S,x), Maximum(S), Extract-Max(S), Increase-Key(S,x,k). • Max-Heap can be used for implementing max-priority queue.

13. Doubly Linked List 1 2 3 prev key next

14. x is an object!!! 1 x 2 1

15. x is an object!!! x 2 3 1 2 1

16. Sentinel • A sentinel is a dummy object that allow us to simplify the boundary condition. • With sentinel, a doubly linked list can be turned into a circular one. • The sentinel nil[L] is placed between the head and the tail.

18. Direct Addressing • Direct addressing is a simple technique that work well when the universe of keys is reasonably small. • Direct-address table is an array in which each position, or slot, corresponds to a key in the universe. • If the universe is large, how to do? • Hashing!

19. Hash Table • Collision resolution by chaining

20. Hash Functions

21. What we learnt in this lecture? • Review elementary data structures