Hello Codeforces community!

I am glad to announce that HackerRank Weekly 18th edition will be held on 22th Nov 2015 at 16:00 UTC. You can sign up for the contest here.

Though what's priceless is solving interesting problems and the thrill of competition, prizes make the competition fierce. Top 10 performers will get a HackerRank T-shirt.

Problems have been set by shef_2318 and tested by CherryTree and wanbo. The contest will consist of 5 problems with variable scoring distribution. We have tried our best to prepare a nice problem set. Hopefully everyone will enjoy. Also, you'll be able to enjoy the detailed editorials written by the setter.

Each day you get to solve a challenge whose difficulty level increases as the week progresses. Challenge score will decrease by 10% every 24 hours. To solve the final challenge, you're given an entire weekend.

Tie-breaking rule: For each challenge, we calculate your solved time, t. [t = submit — open] where submit is the time you submitted the solution, and open is the time you opened the challenge. This way, you do not have to worry about solving the challenge as soon as it becomes available.

Good luck and have fun!