Wednesday, 24 July 2013

International Olympiad in Informatics 2013

I was lucky enough again this year to be selected to represent Ireland at the International Olympiad for Informatics (IOI) 2013. This year the competition was being hosted by Australia, in Brisbane, Queenlands.

Brisbane City
Our team of three, myself, Maciej Goszczycki and Charlie Daly (our team leader) set off from Terminal 2 of Dublin Airport on the 2nd of July. What followed was roughly 30 hours of flights and airports. First to Heathrow, then to Dubai and finally to Brisbane. Needless to say, we were exhausted on arrival. I honestly didn't know what day it was by the end.
My room in Cromwell

We spent a few days in Brisbane city centre getting over our jet lag. Then we were picked up on Sunday morning by an IOI bus, to take us to Univesity of Queensland, where the competition was being hosted this year. We got off at St. John's College to regisiter, where we met with our guide, Gayathri, and got allocated our accommodation. Charlie was staying with the other leaders at St. Leo's College, while Maciej and I were staying at Cromwell's College (ahem).

Monday was our first taste of the competition, when we got to go to the UQ Centre for the practice session. The practice problems this year were certainly far more difficult than the practice problems from IOI 2012 in Italy. Afterwards was the Opening Ceremony. We all boarded buses and headed to "Churchie", a local high school. The ceremony this year was certainly rememberable. The dancing flash-mob by the volunteers was hilarious and very unexpected.

The weird root trees that are
all over the city
On Tuesday was competition day 1 and we set off to the UQ Centre. In true IOI tradition, we queued for a rather decent length of time outside the competition hall, waiting for the competition to begin. Unfortunately, due to some technical issues, the first of many, the beginning of competition was delayed further. Once we eventually got into the hall, it began. The three problems were rather interesting. Dreaming, the first, was a tricky, but rather standard graph problem. The second, artclass, was far more interesting, requiring a heuristic algorithm to determine what class of paintings a given image belongs to. The third, wombats, was widely accepted as the most difficult of the day.

I set into wombats first and around the hour mark had my first submission. It graded and I got the first subtasks points. Leaving that, I decided to try artclass instead. By the time I had 20 or so points gotten in artclass, I began to notice a problem. In every task, my solutions weren't grading. I had a screen full of frozen submissions sitting in front of me. I started to look around and as time went on, I notice more and more contestants doing the same. Sharing a sort of a "Is this happening to you too?" look with the people around me, after about fifteen minutes we had our first announc
ement. Technical difficulties.

I set after dreaming then instead, completing a naive bruteforce solution to test. I submitted it. Little did I know, this submission would not be finished grading by the end of competition, even with the several hours left. More announcements left me further puzzled. With little else to do, artclass was the only problem still grading, so I managed to push that up to 43 points. I then realised what was causing the
slowdown. The time limit for the wombats test cases was 20 seconds. It would only take a few submissions that TLE to jam the server for that problem. The competition was extended by half an hour, but ended in pretty much the same state, with all of my dreaming submissions still grading, and several of the other problems' submissions too.

After day 1, we had our first excursion, to the Sunshine Coast. Our first activity was the beach, where I took some surfing lessons. Apparently it was "freezing" according to the Australians, although in 20+ degrees I didn't really notice. The Underwater World aquarium was next, along with the seal show. Last was lunch in the park.

A Tasmanian Devil at Australia Zoo
Thursday brought competition day 2 which was again delayed, apparently due to some last minute changes to the limits of the game problem. The three problems for day 2 were cave, robots and game. I started with cave, which seamed to be a rather interesting problem. A bruteforce solution with some minor optimizations netted 46 points. With still some hours to go, I started the game problem. Unfortunately, as I later found out, game required the use of segment trees to solve anything other than the first subtask. My bruteforce solution solve the first subtask and I started robots with the last half of the competition to go. A simplistic greedy solution for robots, gained 76 points, failing to solve the last subtask and the second, because of memory limits. This could probably be solved with a different data strucure, but I did not have time to try it.

With the competition days over, along with the appeals process for both days, which was held after the second competition, the whole atmosphere around the colleges became much more relaxed. We had our second excursion on Friday, to Australia Zoo. Orignally started by Steve Irwin's parents, the zoo is pretty amazing. The highlights were definitely being able to pet and hold kangaroos and koalas.

Off for Pancakes
The Closing Ceremony was on Saturday, back to Churchie we went to see the medal presentation. With the farewell barbecue later that evening, the IOI was almost over, as most of the teams were leaving the next day. Another 30 hours from Brisane to Adelaide, then Dubai and finally to Dublin got us home, utterly wrecked and sad it was over.

Richard Forster, president of the IOI IC, was certainly right when giving his speech at the Opening Ceremony. He asked us to think of all the stories we would be telling about the IOI in the future, and that although the competition is important, it's the friends and stories we make that are the most memorable. I certainly enjoyed the nights spent in common rooms playing cards, or jenga. And the times when we snuck over to Grace College because we heard the food was better. Or the trips to the supermarket for Tim Tams. That dinner when we made each other try Vegemite on crackers. The late night trip on the city cat boats to Brisbane city centre to get pancakes. The trips to the park. And most of all, all of the friends I made, whether I had known them from Italy last year, or just met them this year, guides and contestants.
Thanks for a great IOI!

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