1v1 knockout tournaments

Players register, check in during the hour before the start and are seeded by rating into a bracket. Every match is one problem on a clock: the first Accepted wins, or at time the most hidden tests passed. Free to host.

How does a 1v1 knockout work on CodeKairo Battles?

A knockout is a single-elimination bracket of one-on-one coding matches. Players register on the tournament page before registration closes, then check in during the hour before the start; only checked-in players are seeded, by CodeKairo rating, into a bracket the size of the next power of two, with byes for the top seeds. Every match of a round is played on the same problem from the organizer's set, on a clock the organizer chooses — an hour by default. The first accepted solution wins; if time runs out, the most hidden test cases passed wins, then whoever reached that number first, then the better seed. A winner's next match starts a minute after its opponent is known, until the final crowns a champion. Hosting one is free.

How it works

  1. Register, then check in. Register before registration closes, subject to the organizer's rules — an email domain, an invite code or their approval. Check-in opens an hour before the start and closes at the start; only players who checked in are seeded.
  2. The bracket draws itself. Seeds follow CodeKairo rating, highest first. The bracket is the next power of two, byes go to the top seeds, and the top two seeds can only meet in the final.
  3. Win your match. One problem, one clock, one opponent whose best test count you can see. The first accepted solution wins on the spot; at time, the most hidden tests passed does.
  4. Move on, or watch. The next match starts a minute after both of its players are known. The bracket page follows every result, and your placement lands on your CodeKairo profile.

Who it is for

Clubs that want one event with one winner — a freshers' contest, a department championship, the qualifier for a bigger event — and players who would rather beat the person across the bracket than a scoreboard.

Frequently asked questions

How are players seeded in a knockout?
By CodeKairo rating, highest first; players with the same rating are ordered by who registered first. Only players who checked in during the hour before the start are seeded.
What if the number of players is not a power of two?
The bracket is the next power of two and the places beyond the field are byes, which go to the top seeds. No first-round match is two byes, and the top two seeds can only meet in the final.
Which problem is each match played on?
Every match of a round plays the same problem: round one the organizer's first problem, round two the second, and so on — from the first again if there are more rounds than problems.
What happens if a match runs out of time?
Whoever passed more hidden test cases wins; if that is level, whoever reached that number first; if neither submitted, the better seed. A player who never submitted loses to one who did.
Can I see how my opponent is doing?
Yes. The match room shows both players' best number of hidden tests passed, updated every few seconds. Neither player sees the other's code.
When does my next match start?
A minute after both of its players are known — a player who wins early waits for the other side of the bracket to finish.