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Assignment 6: Skip lists

Due: Wednesday, 25 October 2017 by 10:30pm

Summary: You will implement skip lists, a famous randomized data structure.

Purpose: To give you experience working from “the literature”. To help you think more about the power of randomization.

Collaboration (code): You may discuss this assignment with anyone you like, provided you credit such discussion when you submit the assignment. You will learn more if you do most of the coding on your own, but you may choose to submit the code for the assignment as a pair or trio.

Submitting (code): Create a tarball from your code and then mail it to your course instructor with a subject of CSC 301 Assignment (Your Name). You should, of course, substitute your name in that subject.

Evaluation: We will primarily evaluate your work on its correctness (e.g., does it compute what it is supposed to; does it meet the requirements of the assignment); clarity (e.g., is it easy to read, is it well formatted and documented); and efficiency (e.g., does it achieve its goal quickly and with limited resources). These criteria will be modified, as appropriate, for written and coding assignments.

Warning: So that this assignment is a learning experience for everyone, we may spend class time publicly critiquing your work.

Read the following article.

William Pugh. 1990. Skip lists: a probabilistic alternative to balanced trees. Commun. ACM 33, 6 (June 1990), 668-676. DOI=10.1145/78973.78977.

Then implement skip lists in either Scheme, C, or Java. Your implementation should include a procedure that prints out the current state of the skip list. (You may find it easier to print them vertically, rather than horizontally.) You should also provide an appropriate test suite.

Note Although you can easily find some implementations online, you will not gain the necessary understanding if you rely on those implementations. As one of my colleagues says, “There’s a benefit to the ** of debugging a data structure.”