20/20 Hack October

9 day programming marathon

The contest has ended

Are you ready to crack 7 more mind-boggling challenges this month?

The contest hosts 7 challenges which are progressively harder to solve. You'll have to 'unlock' each problem to view and solve the next one for a chance to win a cool prize.

The Prizes

  • Top 10 contestants from global leaderboard will win exclusive HackerRank T-shirts.
  • Challenge winners : Top contestant from every challenge leaderboard will receive a book.
  • Daily winners : A contestant who scores highest that particular day will win an exclusive HackerRank T-shirt. Please note this isn't the same as being first on the leaderboard.


The contest hosts 7 or more challenges. More details about the challenges will be revealed soon.

Editorial from 20/20 Hack September

20/20 Hack September had 1323 participants out of 2967 who signed up for the contest.
Editorials for Sherlock Puzzle, Chocolate Game, Stack Exchange Classifier, Help Mike and Sherlock and the Beast have been published


  • Refer to the scoring documentation here
  • This contest will appeal to programmers who're interested in Algorithmic and Artificial Intelligence challenges.
  • HackerRank admins decision will be final
  • Please refrain from discussing strategy during the contest.
  • Any case of code plagiarism will result in disqualification of both the users from the contest. We've a fairly good plagiarism detector that works at the opcode level.
  • You can code directly on our interface. We support 20 major languages. You can have a look at the environment in which we run your code

20/20 Hack September Winners