## 2019 US Open Contest -- Final Results

The 2019 US Open contest was the final contest of our 2018-2019 season. As our national championship contest, it featured featured algorithmic programming problems that were designed to be quite challenging.

A total of 2993 distinct users logged into the contest during its 4-day span. A total of 2309 participants submitted at least one solution, hailing from 64 different countries:

 1431 USA  409 CHN   89 ROU   36 CAN   24 KOR   23 FRA   22 RUS
22 GEO   20 POL   19 VNM   17 TUN   17 IND   17 BGD   15 SLV
11 MEX   10 DEU    8 SGP    8 MYS    6 TWN    6 TUR    6 JPN
6 GBR    6 AUS    4 THA    4 IRN    4 HRV    4 HKG    4 COL
4 BLR    3 ZAF    3 IRL    3 HUN    3 EST    3 BGR    3 ARG
2 TJK    2 SWE    2 SRB    2 NZL    2 MNG    2 MKD    2 IDN
2 FIN    2 EGY    2 ARM    1 ZWE    1 UZB    1 UKR    1 SVK
1 PRT    1 PRK    1 PHL    1 PAK    1 MDA    1 MAC    1 LTU
1 KAZ    1 JOR    1 GIN    1 ESP    1 CYP    1 CUB    1 CMR
1 ATG

In total, there were 5888 graded submissions, broken down by language as follows:

 2127 C++11
1985 Java
1226 C++
460 Python 3.4.0
57 Python 2.7.6
29 C
4 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 2019 US Open Contest, Platinum

The platinum division had 410 total participants, of whom 319 were pre-college students. We saw quite a few high scores including several perfects --- congratulations to all who performed well in this challenging contest! Results for top scorers are here. As a brief note, the time limit for the "boxes" problem was raised just a bit (to 3 seconds instead of 2 for C++, and 6 instead of 4 for Java), since it was otherwise just a bit too tight for Java submissions.

# 1

Tree Boxes
View problem    |   Solution

# 2

Compound Escape
View problem  |   Test data   |   Solution

# 3

Valleys
View problem  |   Test data   |   Solution

## USACO 2019 US Open Contest, Gold

The gold division had 661 total participants, of whom 572 were pre-college students. All competitors who scored 800 or higher on this contest are automatically promoted to the platinum division. Detailed results for all those promoted are here.

# 1

Snakes
View problem  |   Test data   |   Solution

# 2

I Would Walk 500 Miles
View problem  |   Test data   |   Solution

# 3

Balancing Inversions
View problem  |   Test data   |   Solution

## USACO 2019 US Open Contest, Silver

The silver division had 831 total participants, of whom 685 were pre-college students. All competitors who scored 700 or higher on this contest are automatically promoted to the gold division. Detailed results for all those promoted are here.

# 1

Left Out
View problem  |   Test data   |   Solution

# 2

Cow Steeplechase II
View problem  |   Test data   |   Solution

# 3

Fence Planning
View problem  |   Test data   |   Solution

## USACO 2019 US Open Contest, Bronze

The bronze division had 1288 total participants, of whom 972 were pre-college students. All competitors who scored 850 or higher on this contest are automatically promoted to the silver division -- the cutoff this time is a bit higher than usual since the final problem, "evolution", had only two possible answers and a solution could therefore receive half credit on this problem with no effort. Detailed results for all those promoted are here.

# 1

Bucket Brigade
View problem  |   Test data   |   Solution

# 2

Milk Factory
View problem  |   Test data   |   Solution

# 3

Cow Evolution
View problem  |   Test data   |   Solution

### Final Remarks

I hope everyone enjoyed the contests in our 2018-2019 season, including the US Open contest, which included several especially challenging problems in some divisions. Overall, I'm quite happy with the outcomes of this contest and the season as a whole. From the looks of things, we should have a strong contingent of finalists joining us at our training camp this summer.

Technically, there were only three minor issues with the US Open contest. The platinum "boxes" problem had an error in the problem statement initially that arguments to the setFarmLocation and addBox functions could be as large as 10^5 instead of N; this was corrected quickly and does not look like it affected many submissions. We also had an improperly-configured grader running for a few hours on Saturday, giving incorrect "out of memory" results; this was also corrected and any affected submissions were re-graded. Finally, a small typo in the silver fence planning problem was discovered after the contest, saying that M should be "less than" instead of "less than or equal to" the upper limit of 10^5. We therefore changed the test data to respect this condition and re-graded; we expect this probably had little to no impact on submissions.

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 (particularly the US Open!), 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 Dhruv Rohatgi, Spencer Compton, Travis Hance, Patrick Zhang, and Mark Gordon. 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.

We look forward to seeing everyone again when our next season starts in the fall!

Happy coding!

- Brian Dean (bcdean@clemson.edu)
Director, USA Computing Olympiad