We were invited by the Slovakian Olympiad in Informatics to join their IOI selection for training purposes. From April 30th til May 7th, we thus send a delegation lead by Johannes Kapfhammer and Luc Haller with the participants Joël Huber (Kantonsschule Freudenberg, ZH), Christopher Burckhardt (Mathematisch-Naturwissenschaftliches Gymnasium Rämibühl, ZH), Jijingru Yang (Gymnasium Neufeld, BE) and Rada Kamysheva (Schweizer Alpine Mittelschule Davos, GR). Their impressions of the camp are collected below.
This year we were going to travel to Bratislava by night-train, so we agreed to meet at the Zurich main station at 21:40. I was excited to travel by night-train, as this was a new experience for me. When I first arrived at the main station I was surprised by two SOI leaders, Stefanie and Benjamin. Both of them weren’t going to Slovakia with us, but had come to the main station to see us off. Together we had a fun conversation about various topics, ranging from algorithms to personal stories. When it was time to board the train, we waved goodbye to Stefanie and Benjamin and began our journey to Bratislava.
We arrived in Vienna early in the morning, where we had to take another train to Bratislava. After arriving in Bratislava we made our way to the university, where all the contests would be held. We ate lunch at the university cafeteria and prepared ourselves for the first contest. After a brief introduction to the contest format, the contest began. Three interesting problems awaited us, with three hours to solve them. The most difficult problem involved both graph theory and geometry. Although it was a difficult problem to solve, the task statement is relatively simple to understand. Given junctions on a 2D plane and roads which connect them, find a path from junction A to junction B, such that the maximum turning angle of the path is minimized. If there are multiple paths with the same maximum turning angle, the path with minimum length should be output.
After the contest we went to the hostel, were we unpacked our luggage. Only Luc had been to Bratislava before, so we decided to explore the city. All the houses were painted in bright colours. When it started to rain we decided to go into a restaurant and eat dinner. By the end of dinner it was already very late, so we went back to the hostel as quickly as possible.
In the morning, after a easy breakfast, we arrived the training room, but not in time. So there was no Warm-up any more. The tasks in the morning were not difficult, but very skillful. We had a nice lunch in the school dining hall. It’s lucky that I successfully got white rice for my lunch. Yummy! The tasks in the afternoon were even more difficult. One of them looks like Computing Geometry, but in fact it’s only need a math skills to make it easier to solve. For us, these tasks were very challenging.
After that, we went to the old town to have dinner. It took us long time to looking for the restaurant. On the way to the restaurant, we took a tour of Bratislava Castle. Although it’s very windy, but the view of the castle and river was so nice, especially before the sunset. But it’s unlucky that some parts of the castle were closed. Finally, we chose a local restaurant for dinner, which with a very special decoration. Most of us ordered the roasted duck. Definitely, it can not be the official Peking Duck. It was so huge, but delicious. We took the tram go back to the hotel very late, but we were enjoyed the night in Bratislava.
“I just want to sleep and wait for another difficult day with horrible tasks.” That’s what I said before sleep. But this prophecy came true.
Today the tasks were really hard. At first, we used 30 minutes to solve two easy Warm-Up problems on the paper. After that, the contest started normally. I have successfully got all scores in the morning contest. Most of us were very happy, because we got the pleasent scores. But it became bad after a not very nice lunch for Pasta. The contest in the afternoon was really the hardest one I have ever did. I wasted two hours try to solve the easiest one but got nothing variable. After the contests, we were listening to the solutions. For us, these questions didn’t sound very solvable. The main ideas of tasks were 2-Sat, Suffix Array and Nim Game with difficult tricks.
We went to a Pan-Cake restaurant for dinner. There were at least 20 kinds of Pan-cakes, or with Nutella, or with Sheep Cheese. Each of us ordered the Pan-cakes we want. After a enjoyable dinner, we went to a supermarket for shopping. Just buy some bottles of water! Almost everyone returned to the hotel with a box of mineral water. Now our rooms are full of mineral water. This does not look very harmonious, but funny.
Friday was the most implementing day for me. It is sometimes a bit annoying, though this time it was a very good practice. After 7 hours of contest we went to the city center and decided to take pizza and ice cream. We went for a walk in the park and listened to some music, it wasn’t that good, so we decided to go to the other side of the river. There was a very nice bridge with breathtaking view, so we took a few photos and went home to take some rest.
Saturday 4.5.2019 (Chris)
The morning started as always, we woke up at 7 o’clock, ate breakfast and made our way to the university. Today was different though, because in the afternoon we didn’t have a contest. Although I enjoyed the contests every day, it was tiring and I was looking forward to our free afternoon. I was especially excited because we planned on doing an escape room in the evening.
After the morning contest, we decided to go to one of our favourite restaurants and eat pancakes. The cheddar, bacon pancake was without a doubt my personal favourite. This time I also decided on getting an ice-cream milkshake, mostly because it was advertised as being made with four scoops of ice-cream. It tasted just as good as expected. We still had a lot of time before our escape room in the evening, so we went up to the castle. On our way there we passed a huge wedding. They even had live musicians and a few very large cameras. This time the castle garden was also open. The garden wasn’t too large, but it was still very pretty. The castle itself also looked more impressive from this angle with the garden in front of it.
Because we still had a lot of time until dinner, we decided to explore Bratislava some more. The city is a mixture between new glass buildings and old colourful houses. After a while we started to notice a pattern among the colourful houses, every green house was next to at least one orange house. This observation is probably just a coincidence, but on our whole trip we were not able to find any house where this was not the case. For dinner we had decided on hamburgers. From outside the burger restaurant was literally just a door in the wall with a sign above it, but on the inside it was fairly large restaurant. While everyone else decided to order burgers, I decided on chicken wings. The chicken wings were delicious, but it was impossible to eat them without getting your hands dirty. By the end of the meal my hands were full of barbecue sauce. Luckily the bathroom was just around the corner.
It was finally time for the highlight of the day, the escape room. Because each room was only for up to four people, we split into two groups. One was Luc, Yjjr and I while the other was Johannes, Rada and Joel. Our escape room was about a deadly virus, which we needed to find the cure for. After being stuck at the beginning for a while, we were still able to finish the escape room just in time. There were lots of interesting new problems and it was really fun solving them together.
On Sunday it was raining the whole morning, this day there were some sausages for breakfast. Since it was raining till the evening we didn’t go out for lunch and just ordered pizza. This day was geometry day I would say, though we can say that nearly all days were geometry days :) We had solution presentation with some elements of math and new for me algorithms. We had dinner at bistro, there was good atmosphere and tasty food. It was especially cosy, because it was raining outside. Then we bought some sweets in the supermarket and went home to prepare for the next day.
This morning, we got up at seven as usual and, after breakfast, took the tram to the university. But for the first time in this camp, Misof joined us. He explained us the warmup tasks: In the first one, we were given an array of numbers, we had to find out if there exists a tree with those numbers as the degrees of the vertices and if yes, we had to find out if there was more than just one possibility. And in the second task, we had to design a “fair coinflip”: We had to make sure that no one could cheat. After we solved the tasks, Misof explained us the solution. It turned out to be a case distinction for the first and a hash solution for the second problem. Then the real contest began: there was once again a geometry task! We had to place an antenna to connect the households of Vrsar to the mobile network. And we had to compute the sum of some sequence. Then, after lunch, Misof presented us some solutions and told us, what would happen in the afternoon, because the contest then was going to be different. The contest would be an ACM/ICPC-Style Contest where we had four hours to solve seven tasks and it would take place at a different location. So we took our stuff and followed the others until we arrived at a place called VacuumLabs, where the contest took place. Then the contest started, and we calculated the expectations for a random function, helped a grasshopper cross a sea and planted some potatoes. Nobody was able to beat Misof, but at least we were able to beat some slow-downed versions of him. Afterwards, we didn’t have to search for a place for dinner, because we had already eaten enough Pizza, Chips, and much sweeeeeeeets, so we went to the supermarket to refill our backpacks with sweets. Then we went home, where Jijingru made his noodle-soup and then we went to bed.
After we got up, we had to pack our stuff, because it was our last day and we had to give back our rooms before the contest. For the last time this week, we then solved warmups by teleporting through a dungeon. For the last time this week, we then had contest. In our last contest, the first task was garbage ; - ), and in the second task we had to fight bureaucracy by giving the ministers more salary. Chris really liked the second task: “You can just sit there and implement a lazy segtree. It’s so braindead. It’s like meditating”, he said. But my tree was too lazy to work. Nevertheless, we went to the freefood for the last time, and after lunch, for the last time this camp, Misof explained and then announced the winners in Slovakian. We then got a T-Shirt, said goodbye to our Slovakian friends and brought our baggage to the train station. Then we walked straight to the EscapeRoom for round two. Sadly, Chris, Jijingru, and Luc didn’t make it out of the bunker and so the door is now forever closed. We (Johannes, Rada and me) closely escaped from the laboratory and found the medicine to heal ourselves from the virus. As we had time left, we strolled around and had ice cream, before we went slowly to the restaurant. On the way, we rechecked our train connections for the evening. Although Jijingru found our train connection fast on his phone with google maps, I couldn’t find it. Strange… Nevertheless, we went to the restaurant and had a nice dinner and afterwards we went to the supermarket to get everything we needed for our journey home. So we then went slowly to Bratislava hlavná stanica (Main Station) and there looked on the timetable to find out from which platform our train was leaving. Our train was not on it. We already felt a bit nervous and looked at our phones where google maps showed us that there was a train from Bratislava to Vienna departing 20:15 - But it left from Bratislava-Petržalka. We missed our train. Johannes went to the ticket office to ask for other connections, some of us informed others and Chris was standing there and saying: “So why is no one screaming yet? I probably would, but I don’t want to be the first one.” We then discussed what to do now. We decided that the best thing would be to go to Vienna as fast as possible because Rada had to catch a flight there and all connections are via Vienna. So after we had some difficulties opening a locker with some of our luggage, we took the next train to Vienna. There we said goodbye to Rada and looked for the next connection to Zürich. Luckily, there was a train who left to hours after ours but was to be connected with it in Salzburg and so we would arrive in Zürich in time. We then had one and a half hours left in Vienna. Chris, Johannes, and Jijingru solved even more tasks (How were they even able to after this week?) and Luc and I walked through more or less lively parts of Vienna. At half-past eleven, we then took our train and arrived in Zürich in time.