PPT-Hash Tables

Comp 550 Dictionary Dictionary Dynamicset data structure for storing items indexed using keys Supports operations Insert Search and Delete take O 1 time Applications. Spencer Dawson. Summary. What are rainbow tables?. A time and memory tradeoff in password cracking.. A piecewise approach to one-way hashes. What are the advantages/disadvantages. Best uses. Limitations. Lecture 3. Sets. A . set. is simply a collection of elements. Unlike lists, elements are not ordered. Very abstract, general concept with broad usefulness:. The set of all Google search queries from the past 24 hours. Motivating Applications. Large collection of datasets. Datasets are dynamic (insert, delete). Goal: efficient searching/insertion/deletion. Hashing is ONLY applicable for exact-match searching. Direct Address Tables. Linear Probing. Uri Zwick. Tel Aviv University. Hashing with open addressing. “Uniform probing”. Insert key . in the first free position among.  . (Sometimes) assumed to be a . permutation. To search, follow the same order. Passwords stored in computers are changed from their plain text form to an encrypted value.. These values are called hashes, and there is a unique plain text value for every hash.. A rainbow table is a lookup table offering a time-memory tradeoff used in recovering the plaintext password from a password hash generated by a hash function . . Sections 5.3, 5.4, 5.5, 5.6. 2. Designing a Hash Table. Hash function: establishing a key with an indexed location in a hash table.. E.g. . Index = hash(key) % table_size;. Resolve conflicts: . Need to handle case where multiple keys mapped to the same index.. CIS 606. Spring 2010. Hash tables. Many applications require a dynamic set that supports only the . dictionary . operations . INSERT. , SEARCH, and DELETE. Example: a symbol table in a compiler.. A hash table is effective for implementing a dictionary.. Plan. I spent the last decade advising on numerous cases where hash tables/functions were used. A few observations on . What data structures I’ve seen implemented and where. What do developers think, were they need help. We have:. Discussed techniques for hashing. Discussed mapping down to a given range . 0, ..., . M. – 1. Now we must deal with collisions. Numerous techniques exist. Containers in general. Specifically linked lists. Hash Tables. . . 0. 1. 2. 3. 4. 451-229-0004. 981-101-0002. 025-612-0001. © 2014 Goodrich, Tamassia, Godlwasser. Presentation for use with the textbook . Data Structures and Algorithms in Java, 6. . Outline. Discuss what a hash method does. translates a string key into an integer . Discuss a few strategies for implementing a hash table. linear probing. quadratic probing. separate chaining hashing. n. . . [from the . techspeak. ] (var. ‘hash clash’) . When used of people, signifies a confusion in associative memory or imagination, especially a persistent one.” . . -. The Hacker's Dictionary . Instructor: Lilian de Greef Quarter: Summer 2017 CSE 373: Data Structures and Algorithms Lecture 6: Finishing Amortized Analysis; Dictionaries ADT; Introduction to Hash Tables Today: Finish up Amortized Analysis CSE 373: Data Structures and Algorithms. Thanks to Kasey Champion, Ben Jones, Adam Blank, Michael Lee, Evan McCarty, Robbie Weber, Whitaker Brand, Zora Fung, Stuart . Reges. , Justin Hsia, Ruth Anderson, and many others for sample slides and materials ....