How to Generate a Single-Elimination Bracket When the Player Count Is Not a Power of Two

Tournament brackets look like a list of matchups until the participant count is 6, 10, or 14. Then the missing slots need BYEs, seeds need a consistent distribution, and later rounds must wait for actual winners. I built this generator to make those rules visible instead of asking an organizer to fill gaps by hand. The interesting implementation problem is not drawing boxes; it is keeping identity, seeding, and progression correct when the tree is incomplete. Normalize names before creating matches The input accepts newlines, commas, and their full-width variants. Trimming and a Set remove duplicate tokens: const namesList = computed (() => { const tokens = rawNames . value . split ( / [\n ,，;； ] +/g ) . map (( s ) => s . trim ()) . filter ( Boolean ); return [... new Set ( tokens )]; }); The delimiter regex means a pasted list such as Ada, Ben；Cara becomes three names. Empty lines and accidental spaces disappear before bracket math starts. Set preserves the first occurrence while removing exact duplicate strings. That is a product decision as much as a parsing detail: two real players with the same name must add a team name or number themselves, or the generator cannot distinguish them. Generation refuses fewer than two distinct names. That is better than drawing a one-person “final” and pretending it is a tournament. The original participant list remains text until generation, so editing the textarea does not unexpectedly mutate a bracket that people may already be using. Build the next power-of-two bracket and place BYEs Single-elimination trees are easiest to represent when the first round has a power-of-two number of slots. The helper finds that size: function nextPowerOfTwo ( n ) { let size = 1 ; while ( size < n ) size *= 2 ; return size ; } function seedOrder ( size ) { let order = [ 1 , 2 ]; while ( order . length < size ) { const nextSize = order . length * 2 ; order = order . flatMap (( seed ) => [ seed , nextSize + 1 - seed ]); } return order . slice ( 0