January 2017 Contest -- Final Results

This was our second contest of the 2016-2017 season. A total of 3558 distinct users logged into the contest during its 4-day span. Of those, 2439 participants submitted at least one solution, hailing from 66 different countries:

 1445 USA  229 CHN   64 VNM   53 ROU   50 RUS   49 CAN   43 BLR
   38 IRN   31 IND   25 MEX   24 KOR   23 KAZ   23 FRA   22 UKR
   22 DEU   17 BGR   17 AUS   16 COL   15 SGP   14 THA   13 ITA
   13 BGD   12 POL   11 GRC   10 TKM   10 HRV   10 EST    9 GBR
    8 NLD    8 GEO    8 ARM    7 ZAF    7 IDN    6 TUN    5 TUR
    5 JPN    5 HUN    5 HKG    5 BEL    4 SVK    4 FIN    4 BRA
    3 SYR    3 SRB    3 MYS    3 MNG    3 LTU    3 EGY    3 CUB
    3 BIH    3 AZE    2 TWN    2 NZL    2 MKD    2 LUX    2 KGZ
    2 ISR    2 ESP    2 ARG    1 SVN    1 NPL    1 MDA    1 DOM
    1 CZE    1 CYP    1 AUT

The average participant who submitted code submitted solutions for 2.3 problems. In total, there were 5517 graded submissions, broken down by language as follows:

 1989 Java
 1849 C++11
 1198 C++
  222 Python 3.4.0
  151 Python 2.7.6
   47 C
   36 Pascal

Below are the detailed results for each of the platinum, gold, silver, and bronze contests. You will also find solutions and test data for each problem, and by clicking on any problem you can practice re-submitting solutions in "analysis mode". If you are logged in, you will also see your own specific results below alongside the contest(s) you took.

USACO 2017 January Contest, Platinum

The platinum division had 550 total participants, of whom 384 were pre-college students. Many did quite well in the platinum contest this time around, with a whopping 46 perfect scores, 11 from the USA! Detailed results are here.

1

Promotion Counting
View problem  |   Test data   |   Solution

2

Building a Tall Barn
View problem  |   Test data   |   Solution

3

Subsequence Reversal
View problem  |   Test data   |   Solution

USACO 2017 January Contest, Gold

The Gold division had 654 total participants, of whom 529 were pre-college students.

All competitors who scored 700 or higher on this contest are automatically promoted to the platinum division. Detailed results for those promoted are here.

1

Balanced Photo
View problem  |   Test data   |   Solution

2

Hoof, Paper, Scissors
View problem  |   Test data   |   Solution

3

Cow Navigation
View problem  |   Test data   |   Solution

USACO 2017 January Contest, Silver

The Silver division had 1235 total participants, of whom 1045 were pre-college students.

All competitors who scored 700 or higher on this contest are automatically promoted to the gold division. Detailed results for those promoted are here.

1

Cow Dance Show
View problem  |   Test data   |   Solution

2

Hoof, Paper, Scissors
View problem  |   Test data   |   Solution

3

Secret Cow Code
View problem  |   Test data   |   Solution

USACO 2017 January Contest, Bronze

The Bronze division had 1101 total participants, of whom 865 were pre-college students.

All competitors who scored 700 or higher on this contest are automatically promoted to the silver division -- to all who were promoted, congratulations! Detailed results for those promoted are here.

1

Don't Be Last!
View problem  |   Test data   |   Solution

2

Hoof, Paper, Scissors
View problem  |   Test data   |   Solution

3

Cow Tipping
View problem  |   Test data   |   Solution

Final Remarks

Another strong contest in terms of participation numbers! -- Compared to the January contest last year, participation was about 25% higher this year. The contest ran quite smoothly, with no technical problems, and with reasonable final score distributions in all levels.

The only technical "gotcha" that affected a few competitors was that apparently the Java string split method changed behavior between Java version 7 (which our system uses) and Java 8 (the newest release), so that splitting on an empty string gives a different result (in Java 7, the first element of the resulting array is an empty element, but not in Java 8). This tripped up a number of our competitors, and we will try to upgrade to Java 8 before the next contest to avoid the issue in the future (of course then many working solutions to old contest problems will cease to work properly). It is unfortunate the Java designers saw fit to introduce such a major change in such a common language construct.

For those still waiting to achieve promotion, remember that USACO contests are designed to challenge even the very best students, and it can take a good deal of hard work to excel at them. Remember that the more practice you get, the better your algorithmic coding skills will become! To help you fix any bugs in your code, you are encouraged to consult the official solutions above and to make use of "analysis mode" to re-submit improved versions of your solutions.

A large number of people contribute towards the quality and success of USACO contests. Those who helped with this contest include Mark Gordon, Richard Peng, Travis Hance, Mark Chen, Yang Liu, Delphine Dean, Nick (Huaiyu) Wu, Lewin Gan, Karthik Nair, and Nathan Pinsker. Thanks also to Amy Quispe for helping to maintain our social media presence (Facebook: https://www.facebook.com/UsacoContests, Twitter: (https://twitter.com/UsacoContests), our translators for allowing us to offer this contest in five additional languages, to Clemson CCIT for providing our main contest server, and to our sponsors for their generous support: Usenix, D.E. Shaw, Jump Trading, and Ansatz Capital.

See everyone for the next contest in February!

Happy coding!

- Brian Dean ([email protected])
Director, USA Computing Olympiad
Associate Professor of Computer Science, Clemson University

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