Knockout bracket seeding and byes, explained
How a single-elimination bracket is sized, why seed 1 meets seed 8, who gets a bye with 6 or 13 players, and how a timed one-on-one coding match is decided.
The bracket's size
A single-elimination bracket halves the field every round, so it needs a power of two: 2, 4, 8, 16, 32. With any other number of players the bracket is the next power of two up, and the empty places are byes — a first-round match with one player, who goes through without playing.
| Players | Bracket | Byes | Rounds |
|---|---|---|---|
| 6 | 8 | 2 | 3 |
| 13 | 16 | 3 | 4 |
| 20 | 32 | 12 | 5 |
| 32 | 32 | 0 | 5 |
The seeding order
Seeds are placed so that the strongest players meet as late as possible. In an 8-player bracket the first round is 1 v 8, 4 v 5, 2 v 7 and 3 v 6, in that order down the bracket. The top two seeds are in opposite halves and can only meet in the final; the top four are in different quarters and can only meet in the semifinals.
The order for any size comes from the one before it: each seed s in a bracket of n is paired with n + 1 − s. For 16 players it is 1 v 16, 8 v 9, 4 v 13, 5 v 12, 2 v 15, 7 v 10, 3 v 14, 6 v 11.
Who gets a bye
A bye is simply a missing seed. With 6 players in a bracket of 8, seeds 7 and 8 do not exist, so their opponents — seeds 2 and 1 — go straight through. With 13 players in 16, seeds 14, 15 and 16 are missing and seeds 3, 2 and 1 get the byes. The byes always go to the players who earned the best seeds, and with more than half the bracket filled, no first-round match is two byes.
How CodeKairo Battles seeds a knockout
- Check-in opens an hour before the start and closes at the start. Only players who checked in are seeded, so no-shows leave no holes in the bracket.
- Seeds follow CodeKairo rating, highest first; players with the same rating are ordered by who registered first.
- The bracket is drawn once, at the start, and fills itself in as results arrive.
Deciding a timed coding match
Both players get the same problem and the same clock. The first accepted solution wins on the spot. If the clock runs out with no accepted solution, the player who passed more hidden test cases wins; if they passed the same number, the one who got there first; and if neither submitted anything, the better seed. A player who never submitted loses to one who did — which is also how a no-show is decided.
Round names and placements
Counting back from the end: the Final, the Semifinals, the Quarterfinals, then the Round of 16, Round of 32 and so on. A player's placement is the round they reached — Champion, Runner-up, Semifinalist, Quarterfinalist, Round of 16.