lecture 6 data structures. stack top 2 2 4 4 6 6 8 8 9 9x

Lecture 6 Data Structures

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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.

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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.

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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!

Hash Table• Collision resolution by chaining

Hash Functions

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What we learnt in this lecture?

• Review elementary data structures