2021 December Contest -- Final Results

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

A total of 13781 distinct users logged into the contest during its 4-day span. A total of 11599 participants submitted at least one solution, hailing from 90 different countries:

 5433 USA 3973 CHN  450 CAN  354 KOR  198 IND  127 ROU  117 MYS
   80 VNM   66 SGP   46 BLR   45 HKG   38 IRN   38 ARM   35 POL
   33 TWN   32 ISR   30 RUS   28 DEU   27 TUR   27 FRA   27 AUS
   26 GEO   25 UKR   23 SLV   22 GBR   22 BGD   19 JPN   18 SYR
   12 MNG   12 KAZ   12 CUB   12 BRA    9 MEX    8 THA    8 KGZ
    7 TKM    7 PHL    7 LTU    7 GRC    7 BGR    6 ZAF    6 TUN
    6 SAU    6 IDN    6 HRV    6 ESP    6 CHE    5 SRB    5 NZL
    5 EGY    4 PSE    4 PER    4 NLD    4 EST    4 COL    4 ARE
    3 SVK    3 NGA    3 LUX    3 FIN    3 BEL    2 PRT    2 NOR
    2 MKD    2 MDA    2 MAR    2 MAC    2 CZE    1 ZWE    1 VEN
    1 UZB    1 SWE    1 SVN    1 SDN    1 ROC    1 PRK    1 PAK
    1 LKA    1 LIE    1 ITA    1 ISL    1 IRI    1 GUM    1 DOM
    1 DNK    1 CYP    1 CHL    1 BTN    1 BHR    1 ARG
In total, there were 28220 graded submissions, broken down by language as follows:

11029 C++17
 8253 C++11
 5377 Java
 3308 Python 3.6.9
  212 C
   41 Python 2.7.17

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 December Contest, Platinum

The platinum division had 510 total participants, of whom 319 were pre-college students. Results for top scorers (including 8 perfect scores!) are here. Congratulations to all of the top participants for their excellent results!

1

Tickets
View problem  |   Test data   |   Solution

2

Paired Up
View problem  |   Test data   |   Solution

3

HILO
View problem  |   Test data   |   Solution

USACO 2021 December Contest, Gold

The gold division had 1064 total participants, of whom 729 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

Paired Up
View problem  |   Test data   |   Solution

2

HILO
View problem  |   Test data   |   Solution

3

Bracelet Crossings
View problem  |   Test data   |   Solution

USACO 2021 December Contest, Silver

The silver division had 3676 total participants, of whom 2763 were pre-college students. All competitors who scored 700 or higher (about 12% of participants) on this contest are automatically promoted to the gold division . Note that the "closest cow" problem was re-graded with a slightly higher time limit (3 seconds C/C++, 6 seconds Java/Python) since our coaches deemed the original time limits a bit tight for Java.

1

Closest Cow Wins
View problem  |   Test data   |   Solution

2

Connecting Two Barns
View problem  |   Test data   |   Solution

3

Convoluted Intervals
View problem  |   Test data   |   Solution

USACO 2021 December Contest, Bronze

The bronze division had 9974 total participants, of whom 7673 were pre-college students. All competitors who scored 700 or higher on this contest (about 15% of participants) are automatically promoted to the silver division. The bronze cutoff was set fairly low to account for the fact that the bronze contest this time around did not include any trivial problems (and some problems even included a handful of fun larger cases for a challenge, although solving these was not necessary to achieve a high enough score for promotion).

1

Lonely Photo
View problem  |   Test data   |   Solution

2

Air Cownditioning
View problem  |   Test data   |   Solution

3

Walking Home
View problem  |   Test data   |   Solution

Final Remarks

Welcome to the 2021-2022 season of the USACO! We are thrilled to see such an increase in participation over just last year!

The problem lineup this time around definitely did not skimp on difficulty; even the bronze-level contest required careful thinking to devise sufficiently fast solutions. Despite the challenge of these problems, we still saw a healthy number of promotions at all levels. 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. You will have many more opportunities over the course of the season to work towards promotion. 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, Nick Wu, Richard Qi, Jichao Qian, Danny Mittal, Siyong Huang, Timothy Qian, and Andi Qu. 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: Citadel, Ansatz, X-Camp, TwoSigma, EasyFunCoding, and Jump Trading.

We look forward to seeing everyone again for our January contest.

Happy coding!

- Brian Dean ([email protected])
Professor and Chair, Division of Computer Science, School of Computing, Clemson University
Director, USACO