Department of Computer Science | Institute of Theoretical Computer Science

CADMO - Center for Algorithms, Discrete Mathematics and Optimization

Algorithms Lab HS2020

see also the corresponding entry in the course catalogue


For questions on exercises use the forums on moodle (available from Aug 24, 2020). For administrative questions or for reporting technical problems (with moodle or the judge), use


Prof. Emo Welzl


Ben Fiedler,
Hung Hoang,
Dr. Michael Hoffmann (contact),
Asier Mujika,
Kalina Petrova,
Charlotte Knierim,
Tim Taubner,
Miloš Trujić,
Hoàng Long Truong,
Dr. Manuel Wettstein,
Stefanie Zbinden,
Xun Zou

Time & Place

News: Due the current situation with its social distancing requirements we have decided to teach this course online only this semester. As a platform we will use Zoom. Please check these pages for ETH-specific information and instructions about Zoom.

14-16 Problem of the Week
Sep 21-Dec 14
16-18 Assessments
Oct 13-Dec 8
Sep 16-Dec 9
Oct 15-Dec 10
Sep 18-Oct 9
Oct 16-Dec 11

The orange slots (individual performance assessments) are by appointment only. The blue slots (consulting hours) are completely optional and on demand only. Attendance/participation in the green slots (PotW and tutorials) is recommended. For more details see the section "Organization" below.


The objective of this course is to learn how to solve a problem given by a textual description. This includes appropriate problem modeling, choice of suitable algorithms, and a working implementation in C++.



In this course students learn how to solve algorithmic problems given by a textual, story-like description. We assume knowledge of elementary algorithms and data structures as they are typically taught on the Bachelor level. In tutorials we introduce more advanced algorithms and the usage of some standard libraries for combinatorial algorithms. Students practice their skills by solving weekly exercises. For that they have to understand the problem setting, find an appropriate modeling, choose suitable algorithms, and implement them using C/C++, BGL, and CGAL. The evaluation of the correctness and efficiency of their solutions will be performed by an online-judge which compiles the submitted source-code and runs it on a set of test instances.


This course is a lab: Most of the time is spent working individually on the given problems.

In addition there is a weekly tutorial. These tutorials are not lectures in the classical sense. In particular we will not present theory and proofs there. Instead we rely on the corresponding knowledge gained during your Bachelor studies. The tutorials serve

Occasionally we will work with algorithms and data structures that the students may not have encountered during their Bachelor studies. Such algorithms and data structures will be properly introduced in the tutorials, with a focus on applications rather than on the underlying theory.

Every Wednesday after the tutorial we will hand out problem sets. The students hand in their solutions, using the online-judge, within one week.

Every Monday at 14:00 we post one problem as a "Problem of the Week". In order to score points for this problem, only solutions that are submitted within the following two hours are counted. The goal of this setup is to make students accustomed to exam conditions and provide an early feedback of where they stand.

Three times over the course of the semester every student is invited to an individual performance assessment. The assessment is performed as a one-on-one discussion with an assistant of at most 15min. that centers around a specific problem from the week(s) before. The problem to be discussed is known in advance, and the students should prepare to present both the problem and their solution attempt(s) to the assistant. As part of the discussion, the students receive feedback on where they stand, summarized in a grade on an integer scale from 0 (work in progress) to 2 (well done). In turn, the students give feedback on the same scale as to whether or not they found the assessment and the feedback they received helpful. The time slots for the individual performance assessments come in three windows of three weeks each, starting in Mid October. The administration and time management is handled by an electronic system.


The grade of the course is solely based on the final exam. The exam takes place in a computer room, on two different days, 6 hours each, during the examination session. On both days you have to solve problems similar to those given during the semester.

Every student who completes all three assessments (read: shows up at the specified time and completes the process by giving feedback to the assistant in the electronic system) receives a bonus in form of a quarter-grade (+0.25) on their grade from the final exam.

It is impossible to predict how the social distancing and safety regulations will develop until the exam session. But it seems a safe bet at this point that physical presence will be required to take the exam.


1. Fundamentals (Week 1-4) 2. Advanced Algorithms (Week 4-9) 3. Exam preparation (Week 10-14)

Technical Instructions

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