2021 January Contest Contest -- Final Results

The 2021 January Contest contest featured algorithmic programming problems covering a wide range of techniques and levels of difficulty.

A total of 9569 distinct users logged into the contest during its 4-day span. A total of 8301 participants submitted at least one solution, hailing from 88 different countries:

 4662 USA 1753 CHN  323 CAN  275 KOR  148 IND  112 VNM   83 MYS
   61 BLR   53 ROU   53 GEO   52 ISR   48 POL   40 SGP   34 RUS
   33 FRA   32 IRN   30 UKR   28 TWN   25 DEU   25 AUS   24 TUR
   21 BGD   19 MEX   19 CUB   19 ARM   18 KAZ   18 HKG   18 GBR
   17 COL   16 SLV   14 HRV   13 JPN   12 ZAF   11 MNG   11 IDN
   10 VEN   10 TUN   10 THA   10 GRC    8 ARG    7 SAU    7 LTU
    7 BRA    7 BGR    7 AZE    6 NGA    6 ITA    6 EST    6 EGY
    5 KGZ    5 ESP    4 SRB    4 PHL    3 SYR    3 NZL    3 NOR
    3 NLD    3 MDA    3 MAR    3 CHE    2 TKM    2 PRT    2 LUX
    2 LKA    2 HUN    2 FIN    2 BEL    1 UZB    1 TZA    1 TUV
    1 TJK    1 SVN    1 SVK    1 SOM    1 SDN    1 QAT    1 PRK
    1 PER    1 NPL    1 MMR    1 LVA    1 ISL    1 IRL    1 GHA
    1 DZA    1 CMR    1 BRN    1 ARE
In total, there were 23378 graded submissions, broken down by language as follows:

 8383 C++11
 6467 Java
 4703 C++
 3570 Python 3.4.0
  130 C
  119 Python 2.7.6
    6 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 2021 January Contest, Platinum

The platinum division had 432 total participants, of whom 261 were pre-college students. Just like in December, the platinum contest proved to be quite challenging, with very few high scores. Results for top scorers are here.

1

Sum of Distances
View problem  |   Test data   |   Solution

2

Minimum Cost Paths
View problem  |   Test data   |   Solution

3

Paint by Letters
View problem  |   Test data   |   Solution

USACO 2021 January Contest, Gold

The gold division had 1078 total participants, of whom 805 were pre-college students. All competitors who scored 750 or higher on this contest are automatically promoted to the platinum division. Detailed results for all those promoted are here.

1

Uddered but not Herd
View problem  |   Test data   |   Solution

2

Telephone
View problem  |   Test data   |   Solution

3

Dance Mooves
View problem  |   Test data   |   Solution

USACO 2021 January Contest, Silver

The silver division had 4476 total participants, of whom 3561 were pre-college students. All competitors who scored 800 or higher on this contest (195 of them, from the USA) are automatically promoted to the gold division.

1

Dance Mooves
View problem  |   Test data   |   Solution

2

No Time to Paint
View problem  |   Test data   |   Solution

3

Spaced Out
View problem  |   Test data   |   Solution

USACO 2021 January Contest, Bronze

The bronze division had 5400 total participants, of whom 4173 were pre-college students. All competitors who scored 800 or higher on this contest (1218 of them, from the USA) are automatically promoted to the silver division.

1

Uddered but not Herd
View problem  |   Test data   |   Solution

2

Even More Odd Photos
View problem  |   Test data   |   Solution

3

Just Stalling
View problem  |   Test data   |   Solution

Final Remarks

Another successful contest! Normally participation drops off a bit for the second contest of the season, but I'm happy to see numbers very similar to those from December, with roughly 10K total participants and a maximum of more than 1000 simultaneous users during peak usage. Overall, the contest ran quite smoothly. Results were in line with past contests; the bronze through gold contests were perhaps just a touch easier this time around than in December, but nonetheless still quite challenging!

Language note: After testing a new grading server image during this contest, it looks like we should be able to support C++17 and Python 3.6 by the next contest. We are also considering discontinuing support for Pascal, due to a steady decline in usage --- this contest, no USA students used Pascal, and the number of students who submitted solutions in Pascal was actually less than the number of students who accidentally clicked Pascal as their language of submission, intending something else! Details will be posted on the main page if / when any of these changes officially happens.

For those not yet promoted, remember that the more practice you get, the better your algorithmic coding skills will become -- please keep at it! 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. To help you fix any bugs in your code, you can now re-submit your solutions and get feedback from the judging server using "analysis mode".

A large number of people contribute towards the quality and success of USACO contests. Those who helped with this contest include Benjamin Qi, Spencer Compton, Dhruv Rohatgi, Andi Qu, Shreyas Thumathy, Hankai Zhang, Danny Mittal, Chris Zhang, Nick Wu, and Riya Arora. 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: TwoSigma, D.E. Shaw, and Ansatz Trading, and a new sponsor who we are thrilled to welcome to the USACO family: X-Camp.

We look forward to seeing everyone again for the February contest.

Happy coding!

- Brian Dean (bcdean@clemson.edu)
Professor and Chair, Division of Computer Science, School of Computing, Clemson University
Director, USACO