December 2011 Contest -- Final Results

The USACO 2011 December Contest featured algorithmic programming problems covering a wide range of techniques and levels of difficulty. Click here to see the contest problems and solutions.

A total of 1102 participants competed, from 68 different countries:

 438 USA     79 VNM     76 CHN     40 IRN     34 ROU     31 GEO     27 RUS   
  27 KAZ     26 BLR     22 MEX     16 LTU     16 AUS     15 ARM     14 IDN   
  14 CAN     13 BGR     11 UKR     11 TWN     11 KOR     10 ITA     10 DEU   
   9 YUG      8 TUR      8 SRB      8 HRV      7 TJK      7 MKD      7 FRA   
   7 EGY      7 BRA      6 TKM      6 GRC      6 COL      6 BGD      5 VEN   
   5 POL      5 LVA      5 CUB      4 PER      3 SYR      3 LKA      3 IND   
   3 DOM      3 CZE      2 ZAF      2 THA      2 SWE      2 SVK      2 PRT   
   2 AUT      2 ARG      1 SVN      1 SGP      1 NZL      1 MNG      1 MDA   
   1 LUX      1 JPN      1 ISL      1 GER      1 GBR      1 FIN      1 ESP   
   1 DNK      1 BEN      1 ARE   

The average participant submitted solutions for 2.1 problems. In total, there were 2351 graded submissions, broken down by language as follows:

 1375 C++
  592 Java
  294 Pascal
   55 C
   35 Python

Gold Division Results

The Gold division had 130 total participants, of whom 80 were pre-college students.

Full Gold Results

The gold problems in this contest proved to be quite challenging, with both time and memory constraints creating difficulties for many participants. The only perfect score in the gold division this time belongs to observer Lovro Puzar from Croatia. Congratulations, Lovro, on this remarkable feat! There were no perfect scores among the pre-college participants, but many still turned in impressive scores. The top ten pre-college participants in the gold divison are:

Country   Grad   Name Score
VNM  2012    Huy Tran897
USA  2012    Mitchell Lee846
TWN  2015    Peter Yu833
CHN  2015    Yuetong Wang831
CHN  2012    Wenhan Huang806
BLR  2012    Gennady Korotkevich769
CHN  2012    Martin Token752
SYR  2013    Kinan Sarmini722
USA  2013    Johnny Ho701
CHN  2014    Silly Cross638

The top ten observers are:

Country   Name Score
HRVLovro Puzar1000
POLAdam Karczmarz974
UKRYaroslav Tverdokhlib923
BGDNazmul Hasan897
CZEFilip Hlasek897
CANJacob Plachta703
KAZAli-Amir Aldan703
VNMVuongLinh Nguyen679
DEUAlexander Rass667
DEUFabian Gundlach667

Silver Division Results

The silver division saw 217 total participants, of whom 175 were pre-college students.

Full Silver Results

The three silver problems in this contest required a mixture of standard algorithmic techniques plus "out of the box" thinking. Five pre-college students are to be congratulated for their perfect scores:

Country   Grad   Name
USA  2013    Yimo Chen
IRN  2013    Daniyal Mehrjerdi
CHN  2013    Lei Xu
POL  2012    Bartek Dudek
RUS  2012    Egor Suvorov

along with 3 observers:

Country   Name
UKRIvan Mistreanu
RUSMikhail Mayorov
MKDIgor Kulev

Congratulations on achieving a perfect score on this very difficult contest! All of you are promoted to the gold division for future contests. Promotion to gold is also available if desired for any participant receiving a score of 850 or higher -- please email if you fit into this category and wish to participate in the gold contest in January. (As a note to those who are wondering how promotion criteria are set: every contest is different, so we carefully choose criteria for promotion in each contest after reviewing the problems and results in order to make sure that those who are promoted are fully ready for the challenges of the next division).

Bronze Division Results

A total of 755 participants competed in the bronze division, 597 of them pre-college students.

Full Bronze Results

Congratulations to the 14 pre-college students and 4 observers with perfect scores! The pre-college bronze winners are:

Country   Grad   Name
USA  2014    Brian Shimanuki
VNM  2013    Tung Tran
GEO  2013    Tornike Mandzzulashvili
GEO  2014    Nika Nadiradze
ROU  2017    Pavel Ori
CHN  2013    Pu Chen
TWN  2015    Wei Chen Liao
AUS  2015    Michael Chen
USA  2013    Wenkai Lei
KOR  2014    Yechan Bae
VNM  2014    Linh To Ngoc
CHN  2016    Zhouxing Shi
USA  2014    Douglas Chen
RUS  2012    Alex Gordeev

The bronze observers with perfect scores are:

Country   Name
CHNShimi Zhang
USANick Buelich
VNMPhong Duong Thanh
DNKAnders Roy Christiansen

All participants with perfect scores will be automatically promoted to the silver division for future contests. Those with scores of 900 or greater can also be promoted, if desired; please contact if so.

Final Remarks

This contest appears to have been slightly more challenging than the previous contest, especially at the gold level. However, I am still quite happy with the overall distributions in all three divisions.

Our contest infrastructure continues to improve, with only minor technical issues appearing in the contest. The main technical issue we encountered was a sporadic database connection error between our grader machine and our main server, mostly causing long wait times for feedback for some participants; this should be fixed by the next contest, but to make sure everything is set up properly, we need to take the grader machine off-line for the time being, meaning that "analyis mode" (where you can re-submit your solutions to old contests) will not be available quite yet. Look for this feature after the January contest.

I had a lot of excellent help setting up and running this contest. Many thanks go to Nathan Pinsker and Albert Gu for helping to set up the gold contest, Alex Chen for helping with the silver contest, and Kalki Seksaria for helping with bronze. Other members of the coaching staff who contributed time and expertise include Neal Wu, Mark Gordon, Richard Peng, Ben Cousins, Travis Hance, Chris Corsi, and Chad Waters. 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 are also due 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.

I'll see you all again in the January contest!

- Brian Dean (
Director, USA Computing Olympiad