The Challenge

The bus-driver-planning challenge

You work in the planning department at Big Blue Buses. Every day, for not much money and no glory at all, you take on the challenge of creating an optimum working schedule for Big Blue Buses’ drivers to cover the next 14 days.

The closer your schedule is to optimum, the happier your boss and the drivers will be. A low score means an angry boss and angry drivers.

If you’re interested to be a part of Quintiq, then take up this challenge and show us your skills. Score 85% or above and we guarantee you an interview with our exciting organization.

Earn your wage

It’s a real puzzle, and it looks something like this:

  • There are three bus lines: Line 1, Line 2, Line 3
  • You must allocate two drivers per line per day. One for the morning shift and one for the late shift.
  • A driver can only do one shift per day; early or late.
  • There are eleven bus drivers: A, B, C, D, E, F, G, H, I, J, and K. Some are only qualified to drive on Line 1, 2 or 3, while some are qualified to drive on a combination of two of those lines. Find the qualifications under each driver name in the Shift Planning form.
  • Every driver is entitled to days off. Days off are indicated with dark gray nodes in the Shift Planning form. You can’t assign shifts on days off.
  • Some drivers prefer to take particular days of the week off. This is indicated by light gray nodes in the Shift Planning form. These are preferences, rather than rules.
  • Drivers may prefer to work an early or late shift on particular days. The yellow nodes in Shift Planning form indicate shift preferences.
  • Most drivers dislike working too many late shifts. Therefore, the late shifts should be distributed as fairly as possible among the drivers. You should aim to assign exactly 4 late shifts to each driver over the two-week planning period.
  • According to an agreement with the Transport Workers Union, a driver must not be assigned a late shift followed by an early shift the next day.
  • According to a second agreement with the Transport Workers Union, a driver can only work no more than three consecutive late shifts.

To sweeten the deal, we are even throwing in a tablet for the best score of the month.*

How to Play

The bus-driver-planning challenge
  • You have 1 hour to solve the puzzle.
  • Planning a shift on a particular driver can be done in 2 mouse clicks:
    1. Click on the shift in the shift bank (at the top of the application) and
    2. Click on the day on which you want to plan the shift.

To plan a shift:

  1. Click on the shift you want to plan in the shift bank (on the top part of the application). The system highlights the qualified drivers for the shift (indicated by green rectangles on the driver grid)
  2. Click on one of the qualified drivers (one of the green rectangles) to plan the shift

  • Moving a shift from one driver to another is also done in 2 mouse clicks:
    1. click on the shift you want to replan and
    2. click on the grid of another driver on which you want to replan the shift

To replan a shift on another driver:

  1. Click on the shift you want to replan. The system highlights the qualified drivers for the shift (indicated by green rectangles on the driver grid)
  2. Click on one of the qualified drivers (one of the green rectangles) to replan the shift. Replanning a shift on the day that already has a shift assigned will swap the 2 shifts.

  • Unplanning a shift can be done by clicking on the shift and selecting Unplan from the context menu or pressing the Del button on your keyboard.
  • Press the Submit result button on the application toolbar to submit your result and end the puzzle. This Submit result process will happen automatically when the time is up.

I'm ready


Below is a list of our Top 10 challengers. Can you beat their score and stand the chance to win a tablet? (If there is a tie, the time taken to solve the puzzle will be used as a tie-breaker).

100.0% Richard VAN MERSBERGEN 0:02:23
100.0% Koldo Almandoz Forcen 0:02:38
100.0% qwe123w qwe2e12e 0:02:42
100.0% Paula Fermin Cueto 0:02:44
100.0% nana nana 0:03:13
100.0% Arjan Akkermans 0:14:38
100.0% na na 0:32:59
94.2% Khoo Thien Wern 0:39:30
91.6% Christopher Feldman 0:58:40
91.5% Hong Ming Chang 1:00:00

To sweeten the deal, we are even throwing in a tablet for the best score of the month.*

Terms & Conditions

  1. Participation in this contest is open to persons from all countries. Please note the prize collection restrictions in item 6.
  2. Participants can make a maximum of three attempts at the puzzle using a single account.
  3. Participants who score 85% or above are eligible for a job interview, provided that:
    • They are found to be qualified and suitable for available roles
    • There are vacancies at the preferred Quintiq location
    • They can attend the interview in person
  4. The leaderboard features the 10 highest scores (best timing and best results) of the month. The leaderboard is reset at the start of each month.
  5. An iPad mini is awarded to the winner of the month, provided the score is at least 85%. In the event of a tie, the amount of time taken to solve the puzzle will be used as a tiebreaker. A participant can only win the prize once.
  6. The winner must claim the prize within two months of the announcement, in person, at their nearest Quintiq office. The prize can only be collected at our offices in Europe (The Netherlands, Germany, The Nordics, France and Italy), Malaysia (Kuala Lumpur), China (Shanghai) and Australia (Melbourne). The prize will not be mailed to the winner. The winner is entitled to the prize regardless of the outcome of the job interview.
  7. This competition is not open to Quintiq employees. However, friends and family of employees are welcome to participate.
  8. We trust that all attempts and submissions to this competition are the genuine efforts of the participant alone. Any more than three attempts at the puzzle or registration of more than one account automatically terminates the participant’s eligibility for the prize and job interview.
  9. Quintiq reserves the right to apply the terms and conditions as deemed fit, in addition to taking measures to verify the authenticity of each solution before awarding the prize.
  10. The deadline to submit your score is on the last day of every month, at 24:00, Malaysia local time (GMT +8 hours).

To sweeten the deal, we are even throwing in a tablet for the best score of the month.*

Meet the Winners

Jan Hoogland receiving his new iPad from Birgit, TA Coordinator at Quintiq, 's-Hertogenbosch.

December 2017 Winner

Jan Hoogland

''An old classmate of mine told me about the ComBUStion challenge and that someone with our education should be able to solve it. I was looking for a challenge so I decided to try it out and as it turns out it is indeed possible. Just solving the problem would be too slow to beat the fierce competition however. Solving the problem doesn’t take that much time, actually not even more than a second. Getting the data into the model and getting the solution out of it is what takes up most of the time by far. By automating this process, I solved the puzzle in two and a half minutes. I could have actually done it even faster, as I needed half a minute to fix a bug in my code while the clock was ticking, but luckily that was not necessary to be the winner. I want to thank Quintiq for the iPad but I am even more grateful for how they challenged me to learn new things!''
- Jan Hoogland

Kevin Dalmeijer receiving his new iPad from Loek Huibers, Director at Quintiq, 's-Hertogenbosch.

November 2017 Winner

Kevin Dalmeijer

''I took on the Quintiq ComBUStion challenge, thinking that optimizing the schedule would be the most difficult part. Soon after, I realized that reading in the instance and putting back the result were the main bottlenecks. In my final version, I read in the instance by matching the colors of the pixels on the screen. Next, I solve the scheduling problem with the mixed integer programming solver CPLEX, and finally I use my automatic clicker to put in the solution. Inputting the solution takes some time, because after every click I had to wait for the Quintiq servers to respond. I played around with the idea of tampering with the traffic between my computer and the server, but in the end this was not necessary to win. I would like to thank Quintiq for this great puzzle, which involves more than meets the eye!''
- Kevin Dalmeijer

Joost Linthorst receiving his new iPad from Sandra van Herpen, Recruiter at Quintiq, 's-Hertogenbosch.

October 2017 Winner

Joost Linthorst

''The Quintiq ComBUStion challenge immediately got me intrigued. It builds upon one of my university courses, so I was excited to apply this knowledge. After spending some time, I came up with a model which solved the problem to optimality (actually my 3rd iteration of the model, reading the assignment correctly turned out to be a great challenge as well). The only thing then left to optimize was the time. This included automatically building the problem instance from the screen and clicking in the solution. I also tested several solvers to select the fastest. The competition was fierce, but I am glad I came out on top. Thank you Quintiq for this fun problem and the nice prize!''
- Joost Linthorst

Gerhard van Ginkel receiving his new iPad mini from Arjan Zeeman, Senior Recruiter at Quintiq, 's-Hertogenbosch.

September 2017 Winner

Gerhard van Ginkel

''At the start of my recruitment process at Quintiq, I was invited to participate in the ComBUStion challenge. After examining the puzzle, I figured it could be solved by using mixed-integer linear programming. I implemented the formulation in Java, using the information of the problem formulation and the example. After inputting the appropriate data manually, the Gurobi solver was able to calculate the optimal solution within a second. Luckily, nobody did beat my time, so it was enough for the win this month. The great thing about the ComBUStion challenge is that it is a really fun, challenging and original way to start an application procedure. As a new Quintiq employee, I look forward to solving even more puzzles with my new colleagues!''
- Gerhard van Ginkel

Wouter Merkx receiving his new iPad mini from Arjan Zeeman, Senior Recruiter at Quintiq, 's-Hertogenbosch.

August 2017 Winner

Wouter Merkx

''I got in touch with Quintiq in my study Econometrics and Operations Research, when some guest lectures where given by employees of Quintiq. They gave a clear insight of some optimization problems which were dealt in daily life at Quintiq. At the end of class, the ComBUStion was mentioned as challenge for the interested students. Similar optimization puzzles were treated during my study and therefore I decided to give it a shot. The idea was to solve the problem by linear integer programming and the successful tests on the provided example convinced me that my model performed well. The problem was, however, to import and export the data from the Quintiq application. I hoped that implementing automated clicking systems, what has been done by previous winners, was not needed to end highest in the leader board. Unfortunately, this lead to small mistakes with copying the data in the second and third attempt and this resulted in loss of time. Nevertheless, I was very excited to see at the end of the month that the first attempt was enough to win the puzzle. Thank you Quintiq for the challenging and interesting puzzle!''
- Wouter Merkx

Fester Kroep receiving his new iPad mini from Lieke Schröder-Schreurs, Senior Algorithm Expert at Quintiq, 's-Hertogenbosch

July 2017 Winner

Fester Kroep

''I already came across the ComBUStion a couple of years ago, and it always seemed like a fun problem to solve. Since I am currently looking for a job, this seemed like the perfect time to do just that. After writing down the MIP, I implemented it in C++ and obtained the optimal solution within a second. Since the interesting part for me was to solve the problem, I decided not to bother automing the data input and output process for a better time. Luckily, that was still enough to win this month. Thank you Quintiq, for one of the nicest and most original ways to start an application procedure.''
- Fester Kroep

Naut Bulten receiving his new iPad mini from Hidde Kok, Technical TeamLead at Quintiq, 's-Hertogenbosch.

May 2017 Winner

Naut Bulten

"I found out about Quintiq through a company that makes use of their software. After looking around on the website, I stumbled upon the ComBUStion puzzle. I like puzzles and I'm a competitive person, so I decided to give it a go. At first I tried to solve it manually, but this didn't end up in a perfect solution. Luckily the problem can be formulated as an ILP problem and it isn't too big to have a solver complete it in a matter of seconds. To me the hard part was transferring the data, but even when doing this manually it's possible to have the fastest perfect score (although not in most months!). I liked solving the puzzle and I am grateful for the iPad mini. I'm not looking for a job at the moment, but I'm sure Quintiq will have no problem attracting plenty of talented employees with this puzzle!"
- Naut Bulten

Xiaojie Luan receiving her new iPad mini from Dan Roozemond, Products Optimization Leader at Quintiq, 's-Hertogenbosch.

April 2017 Winner

Xiaojie Luan

"Solving industrial puzzles is always an enjoyable process for me, as it is a good chance to test my analytical capability and enhance my theoretical knowledge. When I came across the ComBUStion competition from my college, I noticed that it is an MILP optimization problem which I have learned in my master study. Without hesitation, I immediately started modelling the problem based on the problem explanation and the example. The modelling part was not easy as it involved several tricky constraints. After several attempts, I can obtain the optimal solution based on my model with a commercial optimizer. Another problem popped up, which was how to input data and output result in an efficient way. Obviously, it can be done manually but suffers low efficiency. Based on the litter hints from previous winners, I decided to develop an automated data input and output system. Finally, I managed to finish all the process within 3:30 minutes. Overall, it is really an enjoyable and challenging puzzle. It not only enables me to test my knowledge but also gives me a chance to learn new knowledge. Thank you very much, Quintiq!"
- Xiaojie Luan

Carl Ahremark receiving his new iPad mini from Andreas Grundsell, Business Unit Director, Nordics at Quintiq, Sweden.

March 2017 Winner

Carl Ahremark

"The first time I came across optimization during my engineering studies I knew that this was something special. From the logical mathematical side to the connection with real planning problems. I was hooked and more courses followed. During that time I figured that working in a field related to optimization and supply chain in particular would be an excellent way to combine work with my passion. With that in mind I stumbled on the name Quintiq in a brochure for a job fair at my university. Upon seeing the word supply chain optimization I immediately went to Quntiqs web page to read more and found this puzzle. Having done similar projects before, creating the model wasn’t too much of a hassle, even though there were some parts more difficult than others. After modeling was complete I had achieved 100%. But time was an issue, creating the data and clicking took around 20 minutes. After making the process of reading data from the application and output the solution automated using mat lab I gave it another try. My main concern for this process was at which speed the client could react reliably, time and caution had to be balanced. Being almost satisfied with the new time and since the end date for this round of competition was closing in I hoped for the best. Overall this was a fun challenge and in my opinion a good way for Quntiq to stand out."
- Carl Ahremark

Sander van Aken receiving his new iPad mini from Dan Roozemond, Products Optimization Leader at Quintiq, 's-Hertogenbosch.

February 2017 Winner

Sander van Aken

"Ever since I was young, I have enjoyed solving puzzles. When a supervisor of a project told me about Quintiq, I also came across the ComBUStion challenge. During my engineering studies, I already got in touch with modelling problems as MILPs during projects and my master thesis. I considered this challenge as a good opportunity to test my skills. A first attempt did not render the optimal solution as my model was tailored (too much) to the provided example. After reformulating some constraints, I managed to find the optimal solution in a second attempt with manual input. Not yet satisfied with the time, I learnt about automating the data input from a screenshot, and automated clicking for output. Hence, the programme managed to solve the problem in less than 30 seconds. During a third and last attempt my computer screen froze during the automated clicking, yet my time was less than 2 minutes. Regardless of the final outcome, I was more than proud of my achievements. Of course, it got even better when I received an email of Quintiq during the second day of my holiday! Altogether, it was a joyful challenge and, in my experience, the nicest and most original way to start an application procedure. Thank you Quintiq!"
- Sander van Aken

Charilaos Barnasas receiving his new iPad mini from Giancarlo Broggio, Solution architect at Quintiq, Italy.

January 2017 Winner

Charilaos Barnasas

"When I learned about the ComBUStion Challenge, I knew it was a puzzle for me. Obviously, scoring less than a perfect 100% was unacceptable to me. During my studies in Mechanical and Industrial Engineering in NTUA, I learned more in the field of Operational Research like heuristic search techniques, constraint, combinatorial, integer, linear and nonlinear programming. But still I had to learn more deeply in order to be sure that my score would compete in a worldwide arena. Although it is not my first time that I have excelled in an international competition, being best in a worldwide competition-puzzle set by Quintiq, the top high-tech company in the field of ultimate puzzles gives me great satisfaction. It is known, the roads of success and knowledge are always under construction and have many great puzzles, so I am looking forward to enjoying greater challenges ahead."
- Charilaos Barnasas

Thom Steenhuis receiving his new iPad mini from Marcel Fransen, Development Manager at Quintiq, 's-Hertogenbosch.

December 2016 Winner

Thom Steenhuis

''During my studies in Econometrics & Operations Research in Groningen, I have learned how to solve different kinds of optimization problems. So, when I came across the Combustion challenge, I thought about giving it a try. In my first attempt, I tried to solve it manually without any optimization tool. Obviously, in this approach, I could not find the optimal solution. For this reason, I decided I could do better and fortunately there were two more attempts available. It was a real challenge to formulate the problem into a mixed-integer linear program, but ultimately I was able to integrate all constraints. The next step was to write a program that could solve it. My goal was to design a Java program that could read out the relevant information from the screen, solve the problem and click in the solution. It was a real thrill to see that my program solved the Combustion challenge with one mouse click.''
- Thom Steenhuis

Jussi Kormu receiving his new iPad mini from Olli Kämäräinen, Business unit director at Quintiq, Finland.

November 2016 Winner

Jussi Kormu

''I was already in middle of a recruiting process with Quintiq when I heard about the ComBUStion challenge. I figured I could enhance my chances to succeed in the recruiting process by scoring 100% on the challenge and getting my name on top of the leaderboard. My initial idea was that the problem could probably be solved by linear integer programming. Some additional research had to be done before I could convince myself that all the rules could be covered with this approach. The next step was to choose good open source tools for the modelling and solving the model. The actual modelling was the hardest part. Eventually my computer could find a 100% solution for the test data in 2 minutes and I was ready to try the real Puzzle. For this problem It took almost 40 minutes for the solver to find an optimal solution. Luckily this left enough time for the data extraction and feeding in the solution. Despite the poor final time I achieved my goal and solved my first ever linear integer programming puzzle. And what a fun puzzle it was. By now I have already received the best price I could imagine. I am a fresh Quintiq employee and I can continue solving interesting puzzles.''
- Jussi Kormu

Agnieszka Lutowska receiving her new iPad mini from Dan Roozemond, Products Optimization Leader at Quintiq, 's-Hertogenbosch.

October 2016 Winner

Agnieszka Lutowska

''Participating in the ComBUStion challenge was real fun, since solving logical puzzles is one of my hobbies. Moreover, this clearly formulated real-life problem gave me a chance to employ my optimization skills. After examining the puzzle, I transformed it into a linear programming problem which I solved using existing software. Thanks to the short computational time, I could easily complete the puzzle within the given time even reading and writing the data by hand. I find the idea of the ComBUStion puzzle great, since it provides an impression of the kind of work done in the company and gives me a chance to see whether such challenges make me tick. Thank you, Quintiq!''
- Agnieszka Lutowska

Joanne Chew receiving her new iPad mini from Daniel Woodford, Business unit director, Australia.

September 2016 Winner

Joanne Chew

"I stumbled across the ComBUStion competition when I was searching for companies that share the same interest as me in solving puzzles with optimization techniques. While browsing at Quintiq website, the ComBUStion puzzle immediately caught my attention. Looking at the leaderboard at that time, I knew in order to obtain the highest score, I need to find the optimal solution, and also solve it as fast as possible. By looking at the size of the puzzle, linear integer programming was the best option for me. This technique was able to find the optimal solution for a puzzle of this size in a short amount of time. So I modeled the problem and solved it with an open source software. I also designed an Excel spreadsheet to speed up the data entering process. ComBUStion puzzle is not only a fun competition; it also encourages people from all over the world to build interest in finding fast and efficient ways to solve puzzles. Thank you Quintiq."
- Joanne Chew

Aleksi Seppänen receiving his new iPad mini from Olli Kämäräinen, Business unit director at Quintiq, Finland.

August 2016 Winner

Aleksi Seppänen

''I have solved this kind of problems during my studies, so I knew I could solve the problem. The challenge was to solve it as quickly as possible. As the problem was not too complex, I decided to model the problem as an integer linear program to make it fast. After I had tested the model by using the "how to play" -example I proceeded to next step, which was to automate the data entry and solution submission. Before the ComBUStion! Challenge I had not written a program, which would extract data from a picture or control the mouse. My goal was to fully automate the process. I did not quite achieve the goal, but as my semi-automatic program read input data from the screen, solved the problem and clicked the solution in less than ten seconds, I was satisfied with the speed. All in all, it was an interesting, challenging and rewarding puzzle, which also helped Quintiq to stand apart. Thank you!''
- Aleksi Seppänen

Márton Makai receiving his new iPad mini from Herman Stel, Business Consultant, Switzerland.

July 2016 Winner

Márton Makai

''This was a really rewarding fun! I love computational challenges, and one-off projects always give me room to try tools I would not try otherwise. Hence, I had to give the ComBUStion puzzle a shot. Needless to say, my goal was not less than winning it. Mathematical optimization is one of my old loves. Some wind has blown us apart long time ago, so modeling this puzzle turned out to be a refreshing exercise. This part is not very hard, however some constraints need a careful reading. But there is always a catch. Assuming you reach 100% score, it is only the speed of your solution which determines your position on the leaderboard. Solving a typical instance takes seconds for a modern solver, but data transfer to and from a solver easily means hundreds of clicks. A lot of the previous winners already mentioned that the latter should be automated. Well, I definitely wanted to avoid that work as much as possible. Though past leaderboards are not public anymore, I vaguely remember that not all previous winners were super-fast. Hence, my "careful" analysis suggested to take some risk, to not automate the output transferring, and to automate reading only about half of the input. If that is not enough, I still have two more shots. Well, the analysis turned out to be right. I played in a lucky month. One attempt of this half baked solution with 15 minutes of clicking was sufficient. Thank you, Quintiq! I wish good luck to the future players!''
- Márton Makai

Bala Ananthanarayanan receiving his new iPad mini from Marijn van Helvoort, Deputy Director at Quintiq, Kuala Lumpur.

June 2016 Winner

Bala Ananthanarayanan

''The software industry today expects the most optimal algorithms/solutions that are real-time, fast and scalable. Solving the Quintiq ComBUStion puzzle certainly sets you up for that glaring reality. I have been solving production scale mathematical optimization problems for a little over a decade now. So when one of my colleagues introduced me to the ComBUStion puzzle, it sounded quite familiar. I quickly wrote a solution roughly within an hour, but there was definitely more work to be done to get a perfect score. It was on my things-to-do list for a while before I actually got to it in June of 2016. I formulated the problem as a Binary Integer Program and implemented that using my favorite optimizer to achieve a 100% score. However the real challenge was achieving my personal target of taking less than 7 mins to solve the puzzle. I built another piece of software that would accept the parameters for that problem instance, call my Binary Integer Program and display the output in a way that can be easily fed into the Quintiq user interface. I finally managed to solve it in 7:02 mins. Overall, it was a thoroughly engrossing experience.''
- Bala Ananthanarayanan

Sander Siemons receiving his new iPad mini from Lieke Schreurs, Senior Optimization Expert at Quintiq, 's-Hertogenbosch.

May 2016 Winner

Sander Siemons

''Already for a few months the words 'Quintiq' and 'ComBUStion' were on my to-do list, placed prominently above my desk. The puzzle immediately sparked my interest when I first found out about this challenge through a college classmate who had won it a few months earlier. When finally diving into the problem, I quickly realized that the time required was of crucial essence to compete. After constructing a BIP model to solve the problem and testing it on the provided example I therefore used simple Excel sheets to help speed up the data entry. After setting the bar, being the first contester of the month, the long wait began which luckily did not affect my position on the leaderboard. The inspiring and challenging puzzle was a great and fun way to show my optimization and modelling skills and to compare to world-wide competitors!''
- Sander Siemons

Xiang Pei Lim is currently based in Brisbane and came to Kuala Lumpur to collect her prize. Here she is receiving a new iPad mini from Quintiq Director, Ng Moon Ho.

April 2016 Winner

Xiang Pei Lim

''I came across the ComBUStion Puzzle while browsing the internet for Operations Research related work placement opportunities. I was intrigued after reading the description of the puzzle and decided to give it a go because I was learning something similar in university at that time. I constructed a mathematical model using the example in the “How to Play” section, but wasn’t sure whether my model was correct. So, I felt grateful that we were given 3 trials to solve the puzzle as I actually detected quite a number of problems in my initial model, which resulted in a completely incorrect solution. Luckily, I had the chance to fix those issues and managed to get the correct solution in my later trial. The biggest challenge for me in the process of solving the puzzle was the data extraction and entry part. Reading the comments from past winners, I realised that many of them had been able to utilise tools to automate their data extraction and entry processes. By doing so, they had managed to solve the puzzle just within a few minutes. However, I didn’t have the knowledge or skills to do it that way. So, I could only do them manually, which takes up a longer time to solve the puzzle. I guess I was very lucky this month as I might have been on a similar level as the other players, giving me the opportunity to win the prize. Thank you for the prize, Quintiq! It has been an enjoyable learning experience for me.''
- Xiang Pei Lim

Bart Beemsterboer receiving his new iPad mini from Arjan Zeeman, Senior Recruiter at Quintiq, 's-Hertogenbosch.

March 2016 Winner

Bart Beemsterboer

''When I started looking for a job after my PhD in Groningen, a colleague told me about the Quintiq ComBUStion puzzle. As difficult puzzles generally challenge me, I became immediately determined to achieve an optimal score in the shortest time of the month. Aside from that, I was excited with the opportunity to show my modeling and optimization skills. I first reproduced the example instance of the puzzle in MS Excel, in order to practice solving the puzzle by hand. As this obviously did not lead to satisfactory results, I developed an optimization model in AIMMS to do the job. I also built an interface to speed up the data entry process. After several months looking for an opportunity to be the fastest player of the month, I finally won the game this March. I found it really enjoyable to solve the ComBUStion puzzle and it brought me even more experience in optimization modeling.''
- Bart Beemsterboer

Artem Stolyar receiving his new iPad mini from Dionysios Stavrakas, Deputy Director BU Oil & Gas Russia at Quintiq, Moscow.

February 2016 Winner

Artem Stolyar

“I am a mathematician, but I see mathematics not only as a professional field. I see it as a lifestyle. When I learned about the ComBUStion puzzle I started with a detailed study of the problem statement. As result I developed a special “Sandbox application” which simulates the ComBUStion original application in order to test different search technics and design a proper search algorithm. Finally, I developed an application consists of three parts: Scanner for getting initial data from the screen, Solver for search the best possible solution and Clicker for posting the result back to the screen. Using this procedure, the optimal solution was found in a couple of minutes. It was a very interesting and complex challenge. And, of course, it was very exciting. Thank you, Quintiq!”
- Artem Stolyar

Rutger Bakker receiving his new iPad mini from Guido Dekker, Recruiter at Quintiq, 's-Hertogenbosch.

January 2016 Winner

Rutger Bakker

''I’ve always liked solving puzzles, so when a friend told me about the Quintiq ComBUStion challenge I became excited immediately. I started to develop a mathematical model to solve the planning problem based on the ‘How to Play’ example. This example was also useful to test the correctness of the model. In order to achieve a time fast enough to compete for the prizes the solver had to be automated completely. In the end, the solver was capable of reading the input from the screen, solving the problem, and processing the output by controlling the mouse. It was very satisfying to see the computer solve the complete problem to optimality. The ComBUStion is a great innovative recruitment challenge that is a lot of fun to participate and the prize is a very nice reward!''
- Rutger Bakker

Michael Hobbel receiving his new iPad mini from Dan Roozemond, Products Optimization Leader at Quintiq, 's-Hertogenbosch.

October 2015 Winner

Michael Hobbel

"When I discovered the ComBUStion challenge it immediately became clear to me that this problem was far more complex than any of the problems that I had encountered during my computer science education. After a couple of days of taking wrong turns and buses, I came up with a theoretical model that did correctly implement all of the required constraints. I then implemented my model and used it to solve the 'How to Play' page example. To my delight it immediately achieved a very fast and -above all- optimal score. Subsequently, the 'live' run went equally well and drove me straight to my final destination: the top of the leaderboard. The ComBUStion challenge was a great way to test my skills and a very fun way to spend my time!"
- Michael Hobbel

Wouter Smeenk receiving his new iPad mini from Koert Munnich, Business unit director at Quintiq, 's-Hertogenbosch.

December 2015 Winner

Wouter Smeenk

''I first learned about the ComBUStion puzzle from a classmate who had also won it a while back. During my study I had encountered many similar problems and it turned out not to be that hard for me to write a mathematical program that could solve the problem to optimality. However this was not sufficient to win because the best solution on the leaderboard was reached only in about 3 minutes. This meant that I had to automize the input and output procedure of my program as well. When I managed to do this, I tested my program using the example and it seemed to be working just fine. To increase my chances of winning I decided to wait until the last day of the month to run my program on the real problem. This turned out to be a good strategy because I beat the best score in my first attempt. For me the ComBUStion challenge was really fun to take part in and in the end it was very rewarding to get the best score of the month''
- Wouter Smeenk

Alexander Overvoorde receiving his new iPad mini from Daphne Noordhoff, Global Recruitment Director at Quintiq, 's-Hertogenbosch.

November 2015 Winner

Alexander Overvoorde

''I first learned about the ComBUStion puzzle in a guest lecture for a planning and scheduling algorithms course. I was immediately eager to put my new skills to the test by modeling the problem and letting the computer solve it for me! The sample problem allowed me to fully prepare and test my solver before starting the first attempt. However, during the first attempt I realised that inputting the problem and solution by hand was very slow and error-prone. That's when I decided to augment my solver to automatically read the problem from the screen and input the solution by controlling my mouse. This allowed me to get an optimal score in just a couple of minutes! The ComBUStion puzzle is a great way to challenge yourself to think outside the box for all those who are interested in optimisation problems!''
- Alexander Overvoorde

Fulvio Cappadonna receiving his new iPad mini from Giancarlo Broggio, Senior Consultant at Quintiq, Roma.

September 2015 Winner

Fulvio Cappadonna

''When you deal with operations research, you cannot resist solving any optimization problem that comes up to you. When I read about the ComBUStion challenge it was immediately clear to me I had to take part in it. I wrote down a mathematical model just a few minutes after reading the problem specifications, but the hardest part was to set up a quick interface for managing input/output data. The competition was very hard and luckily I managed to get the monthly leadership at my last attempt! It was a very exciting game, and a nice way to show off the potentialities of operations research in real-life situations. Also, I really appreciate the cool prize!''
- Fulvio Cappadonna

Pascal Lutter receiving his new iPad mini from Frank Tinschert, Business unit director at Quintiq, Dusseldorf.

August 2015 Winner

Pascal Lutte

''One of my colleagues told me about the ComBUStion challenge. As I read the introduction, I immediately started to build up an optimization model for determining an optimal solution to the planning problem. After improving the data interface and performing some test runs, I was able to solve the puzzle very quick. The ComBUStion challenge is an interesting way to apply for a job interview and it was great fun for optimization specialists to demonstrate their modeling and programming skills.''
- Pascal Lutte

Paul Breeuwsma receiving his new iPad mini from Dan Roozemond, Products Optimization Leader at Quintiq, 's-Hertogenbosch.

July 2015 Winner

Paul Breeuwsma

"I like the idea of getting a job interview by doing some challenge. I read that Google did it once and I searched the internet to look if more companies have used this idea. I didn't find anything, but later I found this website and I gave it a try. It's nice to win in general, but it's even nicer to win an iPad. So I gave it my best and now I have an iPad and they might give me a job. Very nice! If you think you have a chance, I encourage you to take some time to work out a nice strategy and win this game!"
- Paul Breeuwsma

Hendrik Schaap receiving his new iPad mini from David Duinkerken, Business Unit Director at Quintiq, 's-Hertogenbosch.

June 2015 Winner

Hendrik Schaap

"A colleague of mine told me about the ComBUStion challenge. When I checked it out, I was immediately hooked. Studying the detailed problem description, I recognized that it could be solved using methods I learned from university. So I started modelling and spent some time writing a program that would allow me to solve the bus drivers' optimization problem. That my program eventually found an optimal solution was extremely rewarding.

"The challenge was a fun way to see how the theory taught at university could be applied to solve real-world problems. Thank you, Quintiq, for this pleasant distraction from my daily routine."
- Hendrik Schaap

Martijn Hoogendoorn receiving his new iPad mini from David Eaton, Director Quintiq Academy at Quintiq, 's-Hertogenbosch.

May 2015 Winner

Martijn Hoogendoorn

"The best puzzles are often simple to explain, yet require careful thought to solve. The comBUStion puzzle fits squarely into this category. I thoroughly enjoyed coming up with a solution, and the leaderboard made me strive even more for the best score and the fastest time. I can only recommend trying the challenge yourself!"
- Martijn Hoogendoorn

Baptiste Roziere is currently based in Singapore and came to Kuala Lumpur to collect his prize last Friday. Here he is receiving a new iPad mini from Quintiq Director, Ng Moon Ho.

April 2015 Winner

Baptiste Roziere

"As soon as I heard about this challenge, I was eager to try it. I enjoyed modeling and solving the problem and I felt a great sense of achievement when I tested my solution. This puzzle is a smart way to allow people to demonstrate both their interest in optimization and their problem-solving skills. It was by far the most enjoyable recruitment process I have experienced."
- Baptiste Roziere

Walter Sebastian Gisler receiving his new iPad mini from Ruud Verstegen, Business Unit Director at Quintiq, 's-Hertogenbosch.

March 2015 Winner

Walter Sebastian Gisler

"Being fascinated by all kinds of mathematical puzzles and games, I had high ambitions when participating in the ComBUStion challenge. I carefully analyzed the problem and its requirements and then quickly figured out a method that allowed me to optimally solve the scheduling problem. It was great to see how many of the Big Blue Bus drivers' wishes I was able to take into account without violating the agreement with the Transport Workers Union. Quintiq's challenge is not only a lot of fun, it is also a playful representation of some of the company’s daily tasks. Thank you for this opportunity and the cool prize!"
- Walter Sebastian Gisler

Etienne Baghuis receiving his new iPad mini from Tobias Brandenburg, HR Director at Quintiq, 's-Hertogenbosch.

Febuary 2015 Winner

Etienne Baghuis

''The ComBUStion puzzle was the perfect way to show off my modelling and programming skills. The planning problem was related to my master's degree area of study, so solving the puzzle was an interesting challenge. After programming a smart code and introducing a friendly-user interface, I was able to achieve the perfect score in a few minutes. It was a real pleasure to be rewarded as the winner of the month and I would like to thank Quintiq for this great gift. This puzzle was a good way to give me a simplified picture of Quintiq problems and it further motivated me to start a career in operational research.''
- Etienne Baghuis

Jari Keiski receiving his new iPad mini from Olli Kämäräinen, Business unit director at Quintiq, Finland.

January 2015 Winner

Jari Keiski

''The ComBUStion puzzle is a very well thought-out challenge and a clever way to recruit new talent. It gives you a feel of the kind of problems present in planning and optimization. The pursuit of the perfect score against players from around the world is captivating. If you have a problem-solving mind, you cannot really do your victory dance until you know you have found the optimal solution! As it happens, the contest also brought together my two greatest passions since early childhood: flat keyboardless minicomputers, and keeping the wheels on the bus spinning.

Thank you Quintiq!''
- Jari Keiski

Eric Combette receiving his new iPad mini from Franck Mornet, Business Unit Director at Quintiq, Paris.

December 2014 Winner

Eric Combette

"The ComBUStion challenge is a very exciting way to get a job interview at Quintiq. I really enjoyed thinking about how to reach the optimal solution in the minimum time and creating an algorithm able to do so. It made me realize how fun it would be to do that on real-life puzzles. As part of a recruiting process, I think it's a powerful way for the candidates to discover Quintiq's business and to demonstrate their skills in the meantime. Thanks Quintiq for the opportunity and for the prize!"
- Eric Combette

Seren Soner receiving his new iPad mini from Jörgen Nijhof, Manager Corporate Support at Quintiq, 's-Hertogenbosch.

November 2014 Winner

Seren Soner

"The moment I saw the ComBUStion puzzle, I knew I needed to solve it. It was challenging and exciting, and introduced Quintiq's problems in a really simple manner. I immediately modeled the problem, and it really gave me a sense of satisfaction knowing that I found the optimal solution. The iPad Mini is a really good prize, but so is being the winner of a worldwide competition. Thanks Quintiq!"
- Seren Soner

Maximilian Brock receiving his new iPad mini from Maarten Hendriks, Business unit director at Quintiq, 's-Hertogenbosch.

October 2014 Winner

Maximilian Brock

"Only a few seconds after learning about the ComBUStion puzzle, I was already thinking about how to model it. Tackling a complex problem like this at scale is always fun and challenging, especially when it becomes clear that you are participating in a global competition. Encouraging people to demonstrate or even to discover their abilities in a playful environment seems to be an effective recruiting strategy. It certainly gives them a taste of what it would be like to work at Quintiq. Thanks for this opportunity. I'm happy to win the prize this month."
- Maximilian Brock

Francesco Ferrucci receiving his new iPad mini from Frank Tinschert, Business unit director at Quintiq, Dusseldorf.

September 2014 Winner

Francesco Ferrucci

"Solving large puzzles often starts with solving smaller ones. Taking part in the Quintiq ComBUStion puzzle was challenging and engaging. What I enjoyed most was being able try out a real-world task that's related to Quintiq’s business. Such an experience is priceless and the reward makes it that much sweeter. Good idea, Quintiq. This challenge may even help people discover a passion they weren't aware of. Thanks again and keep it up. "
- Francesco Ferrucci

Verena Schmid receiving her new iPad mini from Frank Tinschert, Business unit director at Quintiq, Dusseldorf.

August 2014 Winner

Verena Schmid

"Participating in the ComBUStion challenge is a wonderful way to learn about the types of puzzles Quintiq solves on a regular basis, albeit on a smaller scale. It is amazing how exciting it can be to solve such a real-life planning problem, and it's definitely the most fun I've had in any recruiting process. The fact that you also win a prize by finding the solution in the shortest time makes it even sweeter. Thank you, Quintiq!
- Verena Schmid

Gabriele Chiani receiving his new iPad mini from Giancarlo Broggio, Senior Consultant at Quintiq, Roma.

July 2014 Winner

Gabriele Chiani

"When I found out about the Quintiq ComBUStion puzzle, it became my mission to solve it in the best way possible. I fully enjoyed the resolution process. I have to confess that I was really excited when I verified that the mathematical model I created had found the optimal solution to the problem. I am grateful to Quintiq for acknowledging the work I have done and for the IPad. This puzzle is a perfect way to challenge participants from all over the world and to get to know a smart and fast-growing company such as Quintiq.''
- Gabriele Chiani

Pengfei Zhang receiving his new iPad mini from Jessie Zhao, Office Manager of Quintiq, China

June 2014 Winner

Pengfei Zhang

"The ComBUStion challenge is a perfect combination of entertainment and practical application, which provides a new perspective in understanding Quintiq and the work it does. Not only do you have to solve the puzzle, you have to do it in the shortest possible time. As a global competition, it provides a terrific opportunity for people from all over the world to immerse themselves in this challenge and enjoy the fun that comes with it."
- Pengfei Zhang

Robin Weber receiving his new ipad mini from CEO, Victor Allis

May 2014 Winner

Robin Weber

"When I encountered the ComBUStion puzzle as part of the recruitement process for a Quintiq application, I knew this was a challenge that was right up my alley. The puzzle has some complex features and restrictions, but nothing beats the satisfaction of finding the optimal solution. Of course, I am very proud to be the first European winner of this puzzle, since this was the first month the competition was opened for worldwide competitors."
- Robin Weber

Baraa Al-Bourghli receiving his new ipad mini from Deputy Director, Terry Lim.

April 2014 Winner

Baraa Al-Bourghli

"Ernő Rubik once said, "A good puzzle, it's a fair thing. Nobody is lying. It's very clear, and the problem depends just on you." This is exactly what I experienced while solving the ComBUStion puzzle. It is carefully designed to involve strategic thinking, optimization and attention to detail. It was very enjoyable!"
- Baraa Al-Bourghli

Boo Soon Ting receiving his new ipad mini from HR Director, Alexander Teoh.

March 2014 Winner

Boo Soon Ting

"ComBUStion is both a simple and a very challenging planning puzzle. To make both the boss and Big Blue Bus drivers happy is not an easy job, especially when it has to be done within an hour. The schedule needs to be carefully planned from the start and optimized at the end. I’m curious to know how Quintiq software works to solve its customers’ planning puzzles, which are more complex and span different time zones."
- Boo Soon Ting

Willie Seng Yan Chun receiving his new ipad mini from Director, Yee Meng.

Febuary 2014 Winner

Willie Seng Yan Chun

"I found the puzzle challenge to be an interesting, exciting and competitive program. The puzzle required strong logical and analytical thinking to get the best results. I would like to say thank you to Quintiq for giving me an experience that I never had before and the opportunity to explore what Quintiq is all about."
- Willie Seng Yan Chun

Bavani Meganathan receiving her new ipad mini from Deputy Director, Terry Lim

January 2014 Winner

Bavani Meganathan

"The ComBustion puzzle is really fun and challenging. Addictive too! I can only imagine how exciting it must be for Quintiq employees to work on more complex and larger scale optimization solutions for clients. On a separate note, the puzzle is very user friendly, with clear instructions that make it easy for anyone to understand and attempt. Thank you, Quintiq, for the experience and the iPad!"
- Bavani Meganathan

Lew Ban Choon receiving his new ipad mini from HR Director, Alexander Teoh.

December 2013 Winner

Lew Ban Choon

"It was very rewarding to play Quintiq's ComBUStion puzzle as it exercises my analytical and logical thinking. The puzzle was challenging and it sparked my competitive nature to aim for 100% efficiency. Without a doubt, Quintiq’s ComBUStion puzzle is one of the most innovative ways used for recruitment."
- Lew Ban Choon

Chan Mun Yee receiving his new ipad mini from Director Ng Moon Ho

November 2013 Winner

Chan Mun Yee

"Quintiq's ComBUStion is an interesting and challenging puzzle full of surprises and excitement. I'm thrilled to be a part of this contest and am truly astounded that my efforts have not be in vain. Instead, they have been acknowledged by the prestigious company, Quintiq. Thank you Quintiq for giving me the opportunity to play this awesome puzzle and I'm looking forward to more challenges from Quintiq in the future"
- Chan Mun Yee

Brian Chye Yeong Thean receiving his iPad mini from Deputy Director, Lee Kiew Seng.

October 2013 Winner

Brian Chye Yeong Thean

"Challenging, exciting, and rewarding. There are no better words to describe the Quintiq ComBUStion puzzle. I strongly believe that these 3 words apply and reflect on Quintiq as a company as well. I find the puzzle very intellectually stimulating and, in a way, addictive, as I have constantly pushed myself to do better at the next attempt. It was a good experience having to play the puzzle – thank you Quintiq!"
- Brian Chye Yeong Thean

Li Wei receiving his iPad mini from HR Director, Alexander Teoh.

September 2013 Winner

Li Wei

"Playing the ComBUStion game was a great experience. My logical thinking and analytic skills were challenged. I believe the same logical thinking and analytic skills are what Quintiq is looking for in its future employees, so playing this game gave me a great insight into what Quintiq does and whether I'd fit in. So, I'd like to say thanks to Quintiq for giving me the chance to play this amazing puzzle and to start understanding the company."
- Li Wei

Lam Shin Poh receiving her iPad mini from GDC Deputy Director, Nasreen Izaat.

August 2013 Winner

Lam Shin Poh

"I came across the comBUStion puzzle by chance. I find it very interesting and challenging. It triggered my competitive streak. The application itself is very user friendly and easy to use. Nevertheless, each puzzle requires intense optimization skills and logical thinking. No doubt this is the coolest recruitment process I have ever experienced!"
- Lam Shin Poh

Mathew Tan Honn How, receiving his prize from GDC Deputy Director, Hardip Singh

July 2013 Winner

Mathew Tan Honn How

"Playing Quintiq ComBustion is a very good start to understanding what is Quintiq all about. Besides illustrating prioritization and optimization, the puzzle gives a great insight into the nature of Quintiq's business. Quintiq was the very first company ever to show me what they are all about before I joined them. It's definitely a family everyone wants to be a part of!"
- Mathew Tan Honn How

From Left to Right: Tee Kai Jeff, receiving his ipad mini; CEO, Dr. Victor Allis

June 2013 Winner

Tee Kai Jeff

"My first impression of Quintiq was that it has a gorgeous working environment. I was surprised with its concept of working in a relaxed and fun place. On my first visit to Quintiq, I was greeted by its really nice and professional staff. It was a truly amazing experience and I am looking forward to joining Quintiq."
- Tee Kai Jeff

From Left to Right: Thines, Senior Recruitment Consultant; Cheah Xien, receiving his new iPad mini; Director, Yee Meng.

May 2013 Winner

Oon Cheah Xien

"I find the Quintiq ComBUStion a very interesting and challenging puzzle game. To solve the puzzle, I believe logical thinking and analytic skills are very important as we have to prepare a few steps ahead in order to achieve the most optimized solution. In short, every move counts! Through the puzzle, I'm able to get a rough idea on what optimized planning & scheduling is about and also the challenges behind it. I'm looking forward to more challenges from Quintiq."
- Oon Cheah Xien

From Left to Right: Ana, Recruitment Consultant; Ricky, who can’t wait to start surfing on his new iPad mini; Director, Moon Ho, reluctantly giving up his iPad mini.

May 2013 Winner

Ricky Chea Sin Ong

"This is the best interview experience I've had. Friendly staff, great environment and great bird's eye city view. What else can you ask more from a company? And, the puzzle game is really a creative way to test the problem solving skills of potential employees. Anyone who wants to join Quintiq should challenge him/herself to get the highest score."
- Ricky Chea Sin Ong

From Left to Right: Tan Teck We, receiving his ipad mini; Director, Edwin Cahyadi; Recruitment Consultant, Deveki Sirkunan.

April 2013 Winner

Tan Teck We

"The Quintiq comBUStion challenge is fun and it gives a good overview of what Quintiq's planning and scheduling is all about. I personally enjoy the working environment here, everyone is friendly, helpful and very passionate in what they are doing. It feels like home and I am thankful to be able to join this family."
- Tan Teck We

Chea Sin Li (March’s winner and Quintiq’s newest employee) receiving his prize from Quintiq Director, Ng Moon Ho, accompanied by Recruitment Director, Kavin Ch’ng.

March 2013 Winner

Chea Sin Li

"Quintiq features an awesome working environment that will be fun to work at and it will loosen you up and increase your productivity at the same time. Besides that, the staff is friendly and well-versed. Quintiq has so much to offer and I am looking forward to it."
- Chea Sin Li