The November Long Challenge 2020 was undoubtedly a fun way to start the month. With challenging problems and amazing competition in both Divisions, it was a contest we truly enjoyed. Without any further ado, we present to you the details of the contest that was.
Some Creative Problems.
The Long Challenges always arrive armed with a lot of coding problems, and this time was no different. Division One had nine problems to wade through, and all our skilled players did not disappoint. The most popular problem here was Restore Sequence, as it brought in 881 successful submissions over the ten days. We can only assume that Magical Candy Store was a magical problem as 555 players had solved it before the end of the contest. However, not everything was fun and games for Division One as they saw their fair share of challenging problems. Scalar Product Trees had the players thinking hard as only 160 players managed to solve it. Panic! At the Disco was attempted by around 775 players, but only 20 of these took the green tick home (much like getting tickets to a concert by the legendary American band by the same name). Even more elusive was the problem Selecting Edges. About 600 players sent in answers for the problem, but alas, only15 were successful.
Meanwhile, the coders in Division Two were also hard at work solving the nine problems they were assigned. Ada and Dishes was the problem that garnered the most attention with 12223 successful submissions. The problem Restore Sequence saw quite a lot of action in this Division as well, as over 7950 players solved it. Iron, Magnet and Wall was another problem showered with a lot of love as 4700+ players took home the green tick for it. Talking tough problems for this Division, Chef and The Combination Lock must have had the players scratching their heads as not even 50 coders solved it. Even more frustrating must have been Red-Black Boolean Expression as only seven coders could decode the problem.
Behind The Scenes With The Problem Setter.
After the contest, we got in touch with the problem setter for Chef and The Combination Lock, Anmol Choudhary, and talked to him about his inspiration for the problem,
“I was solving a grid problem, and I misread the problem statement, and after solving the problem I saw that the actual problem was too easy, and I solved another problem. So basically, it gave me the basic idea of the problem. I solved it for N=2 because the grid has a 2-D shape. I came up with an O(N^2) solution and optimized it to O(N log^2N) after learning generating functions”.
Upon being asked how he thought his problem would perform, he said,
“I thought it was an easy problem. I expected it to cross 100 AC’s. but after adding the story in the problem it became slightly hard”.
We have to say, it must have been a fairly hard problem looking at the number of green ticks.
Ranklists Full Of Action
This Long Challenge was privy to some great coding action from both the Divisions. The coder that topped the chart in Division One was rns5. rns5 gained 135 points during the contest and is currently enjoying a personal high score of 2879 points. Clinching the second spot behind rns5 was rgb_icpc2. The player scored a total of 164 points in the competition and was able to use it to jump stars from 5 to 6. Coder rgb_icpc7 claimed the third spot and post this contest qualifies as a 6-star player. In the fourth position, we had participant aurinegro. The Argentinian coder gave a stunning performance to seal a spot in the top 5. Right on his tail, we had user ryodan. Ryodan accumulated 13 points in the contest and is currently enjoying a personal high of 2700 points. The number six spot went to Canadian coder tmyklebu. Despite his outstanding performance, tmyklebu actually ended up losing 5 points during the contest. tmyklebu was followed by player cheng2014, who gave a great display of skill and gained 60 points during the contest. We had a tie for eighth place as both users dario2994, and wasa855 scored exactly 800. At the tenth position, we had coder thuustalu, who gained 124 points in the contest but wasn’t able to jump stars. Although we didn’t have any Indian users in the top 10, players sg1729, spar5h, and anript put up a great show as they secured places 13, 21, and 23 respectively.
Division Two was dramatic with a 7-way tie for the first position. Players rsalesc and krijgertje were able to make this contest count as they both jumped stars from 3 to 4. Next, we had Japanese player memset0. memset0 earned 212 points during the contest and is now a 3-star player. After that, we had coders chasedeath, wlzhouzhuan, and xyr2005, all of whom were able to switch stars from 3 to 4 during this contest. Next was user scimoon, who gained 275 points during the contest and is now a 3-star player. In the eighth position, we had coder lightyear_buzz. The Japanese player accumulated 260 points during the contest and jumped stars from 1 to 3. The number nine spot was the same drama all over again as we had a 15-way tie. You can check out the full ranklist for Div Two here.
Well, that was our recap of the November Long Challenge. We thoroughly enjoyed the contest, and we hope you did too. Until next time this is CodeChef correspondent Riddhi Acharya hoping to see more such fantastic coding in the near future.