'Good hash function' presentation slideshows

Hashtables

Hashtables. David Kauchak cs161 Summer 2009. Administrative. Midterm Be on-time/early Review session SCPD Homework 3 solution Good news and bad news Graders Only Stanford students (i.e. no SCPD) Must have done well on the first homework $13/hr (undergrad), $14/hr (grad).

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Advanced Algorithms for Massive Datasets

Advanced Algorithms for Massive Datasets. Basics of Hashing. The Dictionary Problem. Definition. Let us given a dictionary S of n keys drawn from a universe U . We wish to design a (dynamic) data structure that supports the following operations:

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Distributed Databases

Distributed Databases. CS347 Lecture 13 May 23, 2001. Expected Background. Basic SQL Relational algebra Following aspects of centralized DB Query processing: query plans, cost estimation, optimization Concurrency control techniques Recovery methods. Reading Material.

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Hashing

Hashing. 8 April 2003. Example. Consider a situation where we want to make a list of records for students currently doing the BSU CS degree, with each student uniquely identified by a student number.

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CS305/503, Spring 2009 Hash Tables

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CSCE 310 / 603 Database Systems

CSCE 310 / 603 Database Systems. Chapter 14: Index Structures. Deletion from B-tree. (a) Simple case - no example (b) Coalesce with neighbor (sibling) (c) Re-distribute keys (d) Cases (b) or (c) at non-leaf. n=4. (b) Coalesce with sibling Delete 50. 10 40 100. 10 20 30. 40 50.

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Chained hash tables

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Hashtables

Hashtables. Hashtables. An Abstract data type that supports the following operations: Insert Find Remove Search trees can be used for the same operations but require an order relation to be defined an logarithmic time.

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Hash Table

Hash Table. Introduction. Dictionary : a dynamic set that supports INSERT, SEARCH, and DELETE Hash table : an effective data structure for dictionaries O(n) time for search in worst case O(1) expected time for search. Direct-Address Tables. An Array is an example of a direct-address table

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Hash Tables

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Hashing

Hashing. Lecture based on information from http://www.nist.gov/dads/. Hashing - Terms. A dictionary in which keys are mapped to array positions by hash functions . Having the keys of more than one item map to the same position is called a collision .

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Class Object

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Data Structures and Algorithms

Data Structures and Algorithms. Hashing Dr. Ken Cosh. Review. Sorting Algorithms Elementary Insertion Sort Selection Sort Bubble Sort Efficient Shell Sort Heap Sort Quick Sort Merge Sort Radix Sort. Searching so far.

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CS2110 Recitation Week 8. Hashing

Hashing : An implementation of a set. It provides O(1) expected time for set operations. CS2110 Recitation Week 8. Hashing. Set operations Make the set empty Add an element to the set Remove an element from the set Get the size of the set (number of elements in it)

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CS2110 Recitation Week 8. Hashing

Hashing : An implementation of a set. It provides O(1) expected time for set operations. CS2110 Recitation Week 8. Hashing. Set operations Make the set empty Add an element to the set Remove an element from the set Get the size of the set (number of elements in it)

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Implementation of Linear Probing (continued)

Implementation of Linear Probing (continued). Helping method for locating index: private int findIndex( long key) // return -1 if the item with key 'key' was not found { int index = h(key); int probe = index; int k = 1; // probe number do { if (table[probe]== null ) {

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2003-10-22 Dan Garcia ( www.cs.berkeley.edu/~ddgarcia )

Computer Science 70 Discrete Mathematics and Probability Theory Hashing Lecture 23. 2003-10-22 Dan Garcia ( www.cs.berkeley.edu/~ddgarcia ) inst.eecs.berkeley.edu/~ cs70/ 1 Handout: notes. Big Idea: memoization. General principle: store rather than recompute.

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Hashing

Hashing. Hashing. Many applications require I NSERT , S EARCH and D ELETE functions Hashing on average time can do all of these in O (1) Based on keys Falls under two general categories: Direct-Address Tables Hash Tables. Direct-Addressing. Good for when universe U of keys is small

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Appendix E-A Hashing

Modified. Appendix E-A Hashing. Chapter Scope. Concept of hashing Hashing functions Collision handling Open addressing Buckets Chaining Deletions Performance. What is hashing?.

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Hashing

Hashing. Chapter 10. The search time of each algorithm depend on the number n of elements of the collection S of the data. A searching technique called Hashing or Hash addressing which is essentially independent of the number n.

240 views • 11 slides