USACO US Open 2013 Contest -- Final Results

The USACO US Open 2013 contest, our national champtionship, featured three divisions worth of challenging algorithmic programming problems.

Click here to see the contest problems and official solutions, or to practice re-submitting solutions.

A total of 779 participants submitted at least one solution, hailing from 65 different countries:

362 USA 45 CHN 41 IRN 33 VNM 28 CAN 26 BLR 15 TUR
 15 IDN 14 RUS 13 GEO 12 VEN 11 JPN 10 BEL  7 MYS
  7 BGR  7 BGD  7 ARM  6 UKR  6 THA  6 NLD  6 AUS
  5 TJK  5 ROU  5 KAZ  5 FIN  4 TKM  4 IND  4 FRA
  4 DEU  4 BRA  3 ZAF  3 POL  3 MEX  3 LVA  3 LTU
  3 GRC  3 GBR  3 CUB  2 TWN  2 SYR  2 SVK  2 SIN
  2 MKD  2 KOR  2 DOM  2 CZE  2 AZE  1 YUG  1 SRB
  1 SGP  1 SAU  1 RSA  1 MDA  1 ISR  1 ISL  1 IMN
  1 HUN  1 HRV  1 GER  1 ESP  1 CYP  1 COL  1 BIH
  1 AUT  1 ARG

The average participant submitted solutions for 2.6 problems. In total, there were 2004 graded submissions, broken down by language as follows:

1215 C++
 570 Java
 115 Pascal
  64 Python
  38 C

Gold Division Results

The Gold division had 183 total participants, of whom 159 were pre-college students.

Full Gold Results

The gold division contained three very difficult problems -- quite a bit more challenging than the average USACO contest! There was no easy problem, and as a result, the overall score distribution was quite unforgiving. Nonetheless, four participants earned perfect scores: three pre-college students (Daniyal Mehrjerdi, Ray Li, and Nikolay Kalinin) and one observer (Yaroslav Tverdokhlib). Congratulations to these individuals and all others who turned in impressive scores on this extremely challenging contest! The top pre-college participants were:

Country   Grad   Name Score
AUS  2014    Ray Li1000
RUS  2014    Nikolay Kalinin1000
IRN  2013    Daniyal Mehrjerdi1000
USA  2015    Scott Wu967
RUS  2013    Dmitry Gorbunov900
USA  2013    Johnny Ho900
CHN  2014    Honghua Dong867
USA  2015    Andrew He833
JPN  2014    Kohji Liu833
ARM  2013    Albert Sahakyan767
USA  2013    Ray Li767

and the top observers were:

Country   Name Score
UKRYaroslav Tverdokhlib1000
RUSEgor Kulikov933
CANJacob Plachta767
RUSArtem Rakhov733
GBRRobin Lee700
DEUMaximilian J633
POLAdam Karczmarz567
FINAntti Laaksonen567
VNMKhanh NguyenXuan500
VNMMinh-Hoang Le500

Silver Division Results

The silver division had 210 total participants, of whom 184 were pre-college students.

Full Silver Results

(Note: we've recently re-graded the 'fuel' problem after fixing a small issue with the test data).

Like the gold contest, the silver contest was also quite challenging, with no single problem being particularly easy. Only four participants earned perfect scores: Stefano Chiesa in the pre-college category and Nick Buelich, Alex Anderson, and Topi Talvitie in the observer category. Congratulations to these individuals as well as all our other top scorers. In the pre-college group, top scorers were:

Country   Grad   Name Score
IDN  2014    Stefano Chiesa1000
USA  2015    James Bloxham967
BEL  2013    Victor Lecomte967
IDN  2013    Rakina Zata Amni967
USA  2014    Dan Fu967
JPN  2017    Kotomi Tachibana967
IRN  2014    Mohammad Amin Khashkhashi Moghaddam900
CHN  2016    Zhao Shengyu900
TUR  2014    Kartal Savascisi900
TUR  2014    Metehan Kaya900

The top observers were:

Country   Name Score
USAAlex Anderson1000
USANick Buelich1000
FINTopi Talvitie1000
RUSNikolay Kuznetsov967
CHNPeichen Xie700
COLChrs Zlg667
DEUFabian Henneke667
SYRIjo Ivram667
JPNFiend Friend633
CHNJinglun Li633

All participants with scores at least 700 will be automatically promoted to the gold division for future contests.

Bronze Division Results

A total of 390 participants competed in the bronze division, 327 of them pre-college students.

Full Bronze Results

The bronze contest contained 4 problems of varying levels of difficulty. The most difficult problem, haywire, required very clever insight in order to design a solution fast enough to solve all test cases! Top scorers in the bronze division were the following:

Country   Grad   Name Score
UKR  2015    Yury Monastyrshyn1000
RUS  2014    Nikita Uvarov1000
JPN  2017    Kazumi Kasaura1000
CHN  2013    Yanpei Liu1000
RUS  2013    Ivan Fefer1000
VNM  2013    Hieu Lang1000
FIN  2015    Sami Kalliomäki979
IDN  2013    Joshua Aristo938
IDN  2013    Ammar Fathin Sabili917
BEL  2013    Nathan Meynaert917

Also a round of congratulations to the observers with top scores:

Country   Name Score
RUSDanil Osherov1000
JPNRyoga Tanaka1000
NLDJan Elffers1000
USADaidai Lanlan1000
USACal Che979
USABob Suffern917
CHNXia Jiazhen917
BRAGustavo Segovia900
USAJonathan Paulson875
BLRVlad Sobol863

All participants with scores at least 750 will be automatically promoted to the silver division for future contests.

Final Remarks

This is the final contest of the 2012-2013 USACO season, and perhaps the most challenging as well. I believe it's been a very successful season overall, with contest problems that have been unique, fun, intellectually stimulating, and of the highest quality, thanks mostly to our top-notch coaching staff. I am always impressed at the large number of young participants in our contests who can solve problems that would often be a challenge even to graduate-level university computer science students. To all who have competed this season, you should be proud of your achievements and the commitment you have invested to improve your programming and problem-solving skills.

As I mentioend earler, the US Open is designed to be -- even more than a typical USACO contest -- supremely challenging, even to the very best participants. Do not feel discouraged if your score is not as high as you had hoped! Becoming a world-class algorithmic problem-solver requires patience and practice, and you will certainly improve your skills the longer you keep at it. An excellent way to get more practice is to make use of analysis mode to submit solutions to problems from the past two seasons.

A large number of people contribute towards the quality and success of USACO contests. Those who helped with this contest include Mark Gordon, John Pardon, Richard Peng, Travis Hance, Fatih Gelgi, Jonathan Paulson, Nathan Pinsker, and Josh Alman. Thanks also to our translators and to Clemson CCIT for providing our contest infrastructure. Finally, we are grateful to the USACO sponsors for their generous support: IBM, Usenix, TwoSigma, and Jump Trading.

Based on the results of this season, we will shortly be announcing the list of finalists who will be invited to attend the USACO 2013 summer training camp.

I hope everyone enjoyed the US Open and the entire 2012-2013 season, and I hope to see you back next fall!

- Brian Dean (
Director, USA Computing Olympiad