101 Hack October

4 challenges in 3 hours

The contest has ended

Speed . Accuracy . Efficiency

101 Hack October is here! It's all about speed, accuracy and efficiency. Inside the contest are 4 challenges. You have exactly 180 minutes to solve them. Every second counts.

HackerRank invites you to join the contest to compete against hackers from across the globe.

The Prizes

  • Top 10 contestants will win exclusive HackerRank T-shirts.
  • Rank #1 contestants from each challenge will win "The Beginning of Infinity" by David Deutsch


The contest hosts 4 challenges. More details about the challenges will be revealed soon.

Challenges from 101 Hack Sep

The challenges from the previous contest are here


  • All the challenges will have a predetermined score. Score of a game is calculated using Bayesian Approximation
  • This contest will appeal to programmers who're interested in interesting algorithmic challenges, AI challenges and of course general programming
  • 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

101 Hack Sep Winners