The first contest of the year has just ended, and we’re bringing you all the details you might have missed. From tough problems to a new Division, this is how it all went down this January Long Challenge

A Delicious Platter Of Problems

Division One

The problem set of this Long Challenge was definitely something with all three Divisions being assigned ten problems each. The crowd-favorite problem for Division One was Chef and Ants. With 122 successful submissions and a 19.54 percent accuracy rate, this was the most solved problem of Division One. Other popular problems in Division One included Expected Numbers of SCCs and Guess the Tilling as both got 118 and 72 green ticks respectively.

Speaking about the inspiration behind Guess the Tilling, Author Jay Sharma said,

The tiling of my own kitchen uses the same kind of tiles as given in the problem statement except that the pattern is not random and it looks beautiful. One day, I thought of counting the number of squares formed by them. But there were too many. Obviously, there was a formula but I wondered what if the pattern is random. It wasn’t hard to come up with a linear time solution. But then I thought – What if I gave the number of squares and asked to guess the pattern. I realized that it can become a good CP problem“.

However, not all was fun and games for Division One with the toughest problems of the lot being Curious Matrix and Greedy Students. Curious Matrix was solved by just over 20 players, while Greedy Students was a coder’s worst nightmare as only 6 people cracked the code.

Talking to us about his problem Greedy Students, Setter Sabbir Rahman said,

Initially, I had proposed a different problem which was in the likes of finding k largest paths in a 2-dimensional grid. But since it was a little bit easy, Alei (Contest Admin) suggested trying a different geometric problem. After some discussion, I came up with the problem of finding k largest convex polygons from a set of points. The core idea was still the same as before: finding k largest paths in a weighted DAG. This problem has a solution in the literature. But that solution solves this problem via a different data structure than my solution“.

Division Two

Meanwhile, the most solved problem in Division Two was Fair Elections. With 5295 accurate answers and a 41.6 percent accuracy rate, the problem was every coder’s dream. Watching CPL was another popular problem in the Division with nearly 3000 successful submissions. The problem that had the players scratching their heads once more was Curious Matrix. With merely 2 correct answers, this was a tough one to solve for Division Two.

Division Three

Coming to Division Three, this latest addition to the CodeChef playing field also had quite the party raging. The most popular problem here was Chef and Division 3, which got a grand total of 23,743 green ticks. Another problem beloved to the players was Encoded String as by the end of the ten days the problem had accumulated 19694 correct answers. The mind-numbing problem for this Division was And-Or Game, and by the end of the contest, only 14 people solved the problem.

Action-Packed Ranklists!

The January Long Challenge was full of some great appearances and comebacks. For Division One the player who sat atop the ranklist was 5-star player bigbag . The player gave a stunning performance throughout the contest, and gained 168 points. However, despite this, he wasn’t able to switch stars. The second place was clinched by coder Oleg. The 7-star participant gained 136 points during the contest credit to his solid performance. In the third position, we had player krijgertje. The coder started the contest as a 5-star user and ended it as a 6-star one. Right behind krijgertje, claiming 4th and 5th positions respectively, were players jijiang and itst, both of whom gave us some stunning displays of skill.

The performance of Indian coders in Division One was pretty strong in the contest as coder run_timeterror secured 7th position. Other than run_timeterror we had three other Indian players in the top 15. Participants anript, rivalq and d_en_ominator claimed positions 10, 11, and 13 respectively.

Meanwhile, coder xyr2005 took home the win in Division Two. Credit to the player’s performance, xyr2005 is now a 5-star player in CodeChef. On the second spot, we had American coder watercup. After gaining 204 points in the competition, watercup is now a 4-star player. The next two spots were an all-Indian deal as players sharansh12 and aert claimed 3rd and 4th places respectively. Player aert was able to use this contest to jump stars from 4 to 5. Right behind aert, we had coder jughead (Archie, you there? ). The player gave an amazing display of skills but was unable to switch stars.

The title for Division Three went to Russian coder yank01. The user started the contest as a 1-star player and ended it as a 3-star one. Right behind yank01 we had American player scheffeli. Mirroring yank01, scheffeli was also able to use this contest to jump stars from 1 to 3. In the third place, we had participant szhlg. szhlg gave a stunning performance in their first-ever CodeChef contest and is already a 3-star player. Positions 4 and 5 went to coders denisov and wygzgyw both of whom started the contest as 3-star players and ended it as 4-star ones.

Well, we think we can all agree that the January Long Challenge was the perfect way to start our year. To learn and grow from the competition, check out the video editorials for all the problems.

We hope we have an equally exciting 2021. Until next time, this is CodeChef correspondent Riddhi Acharya.

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