15-295: Competition Programming and Problem Solving, Fall 2017

In this course you will learn the techniques and skills needed to solve algorithmic programming contests problems such as those that appear on the ACM ICPC, Codeforces, and Topcoder. Most of your time will be spent writing programs on your own to solve problems.

Some students may go on to participate in the ACM ECNA regional event (which occurs in the fall) and possibly even the World Finals (which occurs in the spring).

But the skills you will pick up from the course are far more valuable than just enabling you to win contests. Many of the algorithms and techniques are classic ones that every computer scientist should know. You will also learn to think about algorithms in a deeper way, because many of the problems require you have to devise a new algorithm, not just apply a classic one. These skills will be of great value in your other classes, in your job interviews, and in your future work.

Basic Information

Class Meetings: Wednesdays from 6:30-9:30pm, Wean Hall 5421

Instructor: Danny Sleator <sleator@cs.cmu.edu>, Office: Gates 8113, Phone: 412-268-7563

Google 15-295 Group: http://groups.google.com/group/15-295 (Required)

Codeforces 15-295 Group: http://codeforces.com/group/KIrM1Owd8u/contests (Required)

Name List: Put your names here (Required)

Grade Spreadsheet: Tabulation of Scores

For more information on how to join these groups see the Logistics section below.

Weekly Problem Sets

The weekly contests will take place on Codeforces. They are classified under a "Codeforces Group" called 15-295.

The point values of the problems for each weekly contest are tabulated below, along with a solutions page which is based on contributions from students and staff in the class.

#01 Aug 30, 2017: Point values: 1,1,1.5,1.5,2  Problems  contest link  Solutions
#02 Sep 06, 2017: Point values: 0.5,1,1,2,3,3  Problems  contest link  Solutions
#03 Sep 13, 2017: Point values: 1,1,1,2,2,3  Problems  contest link  Solutions
#04 Sep 20, 2017: Point values: 3,1,3,2,2,1,1,3  Problems  contest link  Solutions
#05 Sep 27, 2017: Point values: 1,2,2,2,1,3,1,3  Problems  contest link  Solutions
#06 Oct 04, 2017: Point values: 1,2,2,3,3,3  Problems  contest link  Solutions
#07 Oct 11, 2017: Point values: 1,1,2,2,3  Problems  contest link  Solutions
#08 Oct 18, 2017: Point values: .5,1,1,1,2,2,3  Problems  contest link  Solutions
#09 Oct 25, 2017: Point values: 1,1,2,2,3,3,3  Problems  contest link  Solutions
#10 Nov 01, 2017: Point values: 1,1,2,2,2,3  Problems  contest link  Solutions
#11 Nov 08, 2017: Point values: 1,1,2,2,3,3  Problems  contest link  Solutions
#12 Nov 15, 2017: Point values: 1,1,2,2,2,3,3  Problems  contest link  Solutions
#13 Nov 29, 2017: Point values: 1,1,2,2,3,3  Problems  contest link  Solutions
#14 Dec 06, 2017: Point values: 0(alpha),1,2,2,3,3  Problems  contest link 


This course is 5 units. Each week you will be given several problems to try to solve during class. You will be allowed (for half credit) to solve these problems during the week after the contest ends. You can also get credit for solving problems during rated contests on Codeforces. (This site run rated contests approximately every two weeks.)

Let me be more specific. Each problem that we give has some number of points between 0.5 and 3. Let X be the total number of points of the problems you solve in class. Let X' be the total number points of the problems you solve in the week after class. Let Y be the number of Codeforces problems you solve. (Y only counts problems solved during rated contests. Virtual contests are not rated.) Your score in the course is X + X'/2 + Y.

Here is how your grade is determined:

score ≥ 25: A
score ≥ 15: B
score ≥ 10: C
score ≥   5: D

When you do a Codeforces rated contest, please email me that you have done it so that I can incorporate that into your grade. For Codeforces problems in Div 2, problems A and B are 1 point and the rest are 2 points. For Codeforces Div 1 all problems are 2 points.


You can make use of generic on-line resources while solving problems. These include things like language documentation, API documentation, algorithm descriptions, terminology, etc. You should not search for or make use of code written by others to solve the specific assigned problem.

If you're stuck on a problem, you are welcome to discuss it with another student in the class, or the course staff. Keep the level down so as not to disturb those around you.

During the selection rounds (see below), discussion with classmates is not allowed. Clarifications can be obtained from the course staff.



A great way to get started and to improve is via the USACO training site. They've developed a series of lessons along with corresponding problems. It will take you from a beginner to a strong contest programmer.

There are a number of excellent tutorials on the algorithms and techniques needed to solve these kinds of contest programs on Topcoder's Data Science Tutorials web site.

You can also do old problems on codeforces. Just go to codeforces.com/contests and click "enter" on any of the contests. You can then try solving problems. You can also go to the scoreboard of the contest and click on other people's solutions to see their code. This is a great way to learn.

Feel free to contact (email or stop by) the instructor or the TA any time to discuss problems, including during class.

Here are a few tutorials about important algorithms:

A segment tree implementation and tutorial.
Lecture Notes about min cost flow, along with an implementaiton.
Union-Find Lecture Notes.
Range Trees (AKA Fenwick Trees)
Link-Cut Trees (See detailed comments in this codeforces submission.)

Being on an ACM ICPC Team

We typically send five teams of three to the ACM ECNA regional event. This year it will take place on Saturday October 28. We drive to Youngstown on Friday afternoon, stay in a hotel, do the contest on Saturday, and return in the early evening on Saturday night.

The teams will be selected based on the results of two contests which will take place during regular class times on September 20th and 27th. I am only considering undergraduate students or masters students who are eligible to go to the World Finals (you can't go to the world finals more than two times). The World Finals will take place April 15-20, 2018 in Bejing China. If you are interested in trying to be on a team, it is imperitive that you participate and do well in the two selection rounds on Sept. 20th and 22nd.

Danny Sleator
Last modified: Mon Dec 18 9:08:42 2017