The Chinese University of Hong Kong
Department of Computer Science & Engineering

CSCI5320 (Spring 2022)

Topics in Graph Algorithms


Announcements

2022.4.26 Final Exam Submission: Upload

Final Exam: Exam Paper.

2022.4.19 Final Exam: Open book by ZOOM (April 26, Tuesday 2-4pm).

Exam questions are no harder than homework questions, and the style of the exam is similar to Sample Exam Quesions.

2022.4.19 HW3 submission (due 5pm April 19): Closed

Late submission until 6pm with 20% deduction of marks.
In case you're unable to upload your file successfully, please email it Su Chong (csu@cse.cuhk.edu.hk) with subject "5320HW4-SID".

2022.4.08 Homework 4 posted (due 5pm April 19)

2022.3.22 HW3 submission (due 5pm March 22): Closed

Late submission until 6pm with 20% deduction of marks.
In case you're unable to upload your file successfully, please email it Su Chong (csu@cse.cuhk.edu.hk) with subject "5320HW3-SID".

2022.3.08 Homework 3 posted (due 5pm March 22)

2022.3.01 Pre-recorded lectures for the next two weeks (W9 and W10) are available under Lecture Notes, just in case.

2022.3.01 HW2 submission (due 5pm March 1): Closed

Late submission until 6pm March 1 with 20% deduction of marks.
In case you're unable to upload your file successfully, please email it Su Chong (csu@cse.cuhk.edu.hk) with subject "5320HW2-SID".

2022.2.16 All lecture videos are available under Lecture Notes, and you can watch these lectures together with lecture notes in case I'm unable to teach online because of the worsening COVID-19 situation.

2022.2.15 Homework 2 posted (due 5pm March 1)
Submission of HW2-Q1 (5pm 21 Feb): Closed


2022.2.08 Homework 1 submission: Closed

Late submission of HW1 until 8pm Feb 14 with 50% deduction of marks.
In case you're unable to upload your file successfully, please email it Su Chong (csu@cse.cuhk.edu.hk) with subject "5320HW1-SID".

2022.1.25 Homework 1 posted under "Assignments" (due 5pm Feb 14).

2022.1.24 Online class until further notice.
Zoom Class: https://cuhk.zoom.us/j/709267134?pwd=T3FFTXFiMWhsRk1QbDRRSTJ2RFRoZz09
Meeting ID: 709 267 134 Passcode: 009941

2022.1.21 Notes 2 and 3 updated.

2022.1.07 First Class.

Graphs are everywhere. Do you see graphs and graph problems from the following: 3D printing, Rubik's cube, and pearl necklace?

How many vertices do you need as a certificate to convince a friend that a graph contains a k-vertex cover, i.e., k vertices that cover all edges?

For a computer monitor where each pixel has one of three colours, how to find in no time two same-coloured pixels of distance d apart?

What problem does the following algorithm solve? Randomly mark each vertex of a graph, and return neighbours of marked vertices as output.


Course Information

Lecture: M10:30-12:15 (Wu Ho Man Yuen 303) and T10:30-11:15 (Lee Shau Kee 302) by Prof. CAI Leizhen (Office hours: TBA)

Tutor: SU Chong (Office hours: TBA) csu@cse.cuhk.edu.hk

Grading scheme (tentative): Homework (50%), and Exam or Course Project (50%)


Course Outline

The course discusses fundamental graph algorithms and FPT (fixed-parameter tractable) algorithms. We focus on creative ideas and useful techniques in designing graph algorithms, for instance, a general greedy paradigm for minimum spanning trees, Johnson's reweighting technique for shortest paths, and interesting applications of network flows.

For about 2/3 of the course, we will discuss FPT algorithms for solving NP-hard graph problems. An FPT algorithm confines the exponential time of an algorithm for an NP-hard problem to some part of the input, called parameter k, and therefore solves the problem efficiently for small k, which can be very useful in practice. For instance, the classical problem of finding a vertex cover of size k in an n-vertex graph can be solved in time O(1.2738exp(k) + kn) by an FPT algorithm of Chen, Kanj and Xia (2005), which makes the problem solvable in practice for graphs with 1,000,000,000,000 vertices as far as k < 150. We note that a straightforward exhaustive search algorithm takes around O(n exp(k)) time, which can hardly handle instances with n = 100 and k = 10.

We will discuss various tools for designing FPT algorithms: from basic tools (bounded search tree, and kernelization) to novel tools (iterative compression of Reed, Smith and Vetta, colour coding of Alon, Yuster and Zwick, and random separation of Cai, Chan and Chan). We will also discuss the theory for fixed-parameter intractability, which is akin to the theory of NP-completeness.

Prerequisite: CSCI2110 and CSCI3160 or their equivalents.


References

  1. R.G. Downey and M.R. Fellows, Fundamentals of Parameterized Complexity, Springer-Verlag, 2013.
  2. R. Niedermeier, Invitation to Fixed-Parameter Algorithms, Oxford Press, 2006.
  3. J. Kleinberg and E. Tardos, Algorithm Design, Pearson Education, 2006.
  4. T. Cormen, C. Leiserson, R. Rivest, and C. Stein, Introduction to Algorithms, MIT Press, 2001.
  5. Selected journal and conference papers.