Arena 2y Anniversary

Arena Celebrates its 2 years anniversary with a rated contest !

You will be given 3 problems in IOI style and 2.5 hours to solve them, you will need to read from stdin and output to stdout.

Problems will have two or more subtasks, solving subtasks gives you partial score.

Your score will be the sum of your scores on each subtask over all submissions.

Ties are broken by summing the submissions times of the most recent total score-changing submissions.

Problems were prepared and tested by Nabil many thanks to him.

We wish you a higher rating.


Problem Points AC Rate Users
Mexes 100p 14.1% 9 Editorial
Reverse Xor 100p 14.0% 5
Bitwise swaps 100p 23.4% 10 Editorial


  • 0
    StackBointer  commented on Dec. 19, 2021, 6:41 p.m.

    test date is weak ! my solution has a \(O(n^2)\) time complexity and managed to pass all the test cases !

  • 5
    dauom  commented on Dec. 13, 2021, 3:58 p.m.


    • 0
      moncef  commented on Dec. 26, 2021, 9:12 p.m.

      There were published, open each problem and go to the editorial section

  • 0
    Jalalium  commented on Dec. 12, 2021, 8:45 p.m.

    I get

    "An internal error occurred while grading, and the MOI Arena administrators have been notified. In the meantime, try resubmitting in a few seconds."

    when i try to submit!

    • 1
      moncef  commented on Dec. 12, 2021, 8:51 p.m. edited

      That was corrected and all submissions were rejudged.

      If you want this round to be unrated for you, send an email to