US Open 2012 -- Final Results

The USACO 2012 US Open Contest featured algorithmic programming problems covering a wide range of techniques and levels of difficulty. As the "national championship" contest for the USACO, the US Open is one of the key factors used to determine the set of finalists to be invited to the USACO summer training camp.

Click here to see the contest problems and solutions.

A total of 632 participants competed, from 63 different countries:

294 USA 66 CHN 24 VNM 21 GEO 19 IRN 16 CAN 13 ARM
 12 TUR 11 BLR 10 UKR  9 KAZ  9 BGR  9 BEL  7 RUS
  6 VEN  6 HKG  6 FRA  5 TKM  4 IDN  4 GRC  4 CUB
  4 AUS  3 TJK  3 SRB  3 MKD  3 MEX  3 DEU  3 BGD
  2 ZAF  2 TWN  2 SYR  2 SWE  2 ROU  2 POL  2 ITA
  2 IND  2 CZE  2 BRA  2 AUT  2 ARG  1 THA  1 SVK
  1 SHN  1 SGP  1 PRT  1 PER  1 LVA  1 LTU  1 KOR
  1 JAP  1 ISR  1 IRL  1 IRI  1 IMN  1 GRL  1 GBR
  1 EST  1 DOM  1 COL  1 CHL  1 BRN  1 AZE  1 AFG

The average participant submitted solutions for 2.5 problems. In total, there were 1617 graded submissions, broken down by language as follows:

    909 C++
    499 Java
    116 Pascal
     64 Python
     29 C

Gold Division Results

The Gold division had 127 total participants, of whom 96 were pre-college students.

Full Gold Results

This was one of our most challenging contests to date, with three difficult problems to solve in five hours. Congratulations to our top 10 student participants listed below for their fantastic results, especially to our three perfect scores: Scott Wu from the USA, Mingda Qiao from China, and Gennady Korotkevich from Belarus!

Country   Grad   Name Score
USA  2015    Scott Wu1000
CHN  2014    Mingda Qiao1000
BLR  2012    Gennady Korotkevich1000
USA  2014    Steven Hao857
USA  2013    Johnny Ho824
CHN  2013    Ruosong Wang802
CHN  2013    QiLin Dong788
UKR  2012    Vitaliy Herasymiv784
BLR  2013    Sergey Kulik772
CZE  2013    Stepan Simsa762

The top 10 results in the observer category included two perfect scores as well:

Country   Name Score
DEUFabian Gundlach1000
ZAFBruce Merry1000
RUSEgor Kulikov968
UKRYaroslav Tverdokhlib879
VNMDat NguyenThanh794
THAVisit Pataranutaporn762
VNMThinh FanVan727
CANJacob Plachta664
CHNZechao Shang664
USAJohn Nevard625

Silver Division Results

The silver division had 122 total participants, of whom 105 were pre-college students.

Full Silver Results

Like the gold division, the silver division also proved to be quite challenging, with only 2 perfect scores in the pre-college group. The top 10 pre-college participants are listed below -- congratulations to all for their excellent results!

Country   Grad   Name Score
SRB  2014    Ivan Stosic1000
USA  2015    Andrew He1000
CHN  2014    Kefan Lv939
CHN  2013    Zhizhi Chen848
USA  2013    Cheng Zhang806
USA  2014    Brian Shimanuki800
USA  2013    Sunny Nahar782
USA  2014    Qingqi Zeng762
VNM  2012    Yên Thanh Lê762
CHN  2013    Jiayu sun758

One perfect score also appears in the top 10 list of observers:

Country   Name Score
CUBRamon Alejandro Reyes Fajardo1000
HKGKN Hung782
CUBLeandro Castillo673
VNMTrung Dinh578
HKGHackson Leung578
CHNJacob Jiang578
CHNJiang Jying467
MKDVasja Pavlov412
GBRRobin Lee378
ZAFAshraf Moolla364

All participants with scores at least 667 will be automatically promoted to the gold division for future contests (starting next season).

Bronze Division Results

[Note: the scores on the 3lines problem have changed slightly due to 4 buggy test cases that have now been corrected.]

A total of 383 participants competed in the bronze division, 328 of them pre-college students.

Full Bronze Results

Congratulations to the 2 pre-college students with perfect scores: Alejandra Alfonso from Chile and Johan Sannemo from Sweden! The top 10 pre-college bronze participants are:

Country   Grad   Name Score
CHL  2013    Alejandra Alfonso1000
SWE  2014    Johan Sannemo1000
AUS  2012    Yujin Wu977
CHN  2014    Minyang Jiang966
CHN  2014    Xinyan Hong942
USA  2015    Hariank Muthakana932
USA  2014    Andrew Bent932
USA  2015    Matthew Savage919
SRB  2013    Bojan Rosko917
VNM  2014    Hung Cao Xuan886
LVA  2013    Ojārs Vilmārs Ratnieks886

The top 10 bronze observers are:

Country   Name Score
CHNWei ZiQing988
VNMMinh-Hoàng Lê977
KAZNurlan Zhusupov886
CHNChao Fang864
CHNCarl Pan864
CHNTiny Lic781
CANPaul Liu746
IRNArmin Vakily733
USAZoli K686
CHNTong Pei682

All participants with scores at least 667 will be automatically promoted to the silver division for future contests (starting next season).

Final Remarks

This contest brings to a close what I think has been a very successful season of USACO contests. The US Open was definitely one of the more challenging contests we have ever offered, but students certainly managed to rise to the occasion and come up with strong results. I am glad that there were a few (but not too many) perfect scores in each division -- exactly the sort of distribution we were hoping to see. Technically, everything went smoothly during the contest. Our new infrastructure has matured to the point where it is now mostly stable, and ready to finally see enhancements (evaluation mode, more problem types like interactive and output-only problems, batching of test cases, etc.). Now that the season is finally winding down, we will have plenty of time to tackle these enhancements, as well as moving the training pages to the new site.

This contest would not have been possible -- and it certainly would not have been nearly as high-quality -- if not for the help of a number of remarkable individuals on our coaching staff. Thanks especially to Neal Wu, Mark Gordon, Fatih Gelgi, Travis Hance, Bruce Merry, Richard Peng, and Eric Price for helping with problems, solutions, and test data. These folks did a fantastic and thorough job; for example, they developed more than a dozen solutions to the "balanced subsets" gold problem to make sure they had strong test data. As always, if you would like to contribute to USACO contests as well by sending me high-quality problems, please do not hesitate to do so! Thanks also to Chad Waters and the Clemson CCIT staff for their help with our contest infrastructure, to our translators, who help increase the reach of our contests dramatically, and finally to our sponsors, whose support is absolutely crucial and much appreciated: IBM, Usenix, TwoSigma, and Jump Trading.

The decision on which finalists are to be invited to the USACO summer training camp will be announced very soon.

Happy coding!

- Brian Dean (
Director, USA Computing Olympiad