Count tournament rounds
A single-elimination tournament keeps halving the field until one champion remains. How many rounds does that take?
- Each round pairs up as many teams as possible; odd teams get a bye.
- The number of teams per round is ceil(teams / 2).
- One team or fewer needs zero rounds.
TournamentRounds(teams: int) → int
C# needs a compiler and Drill does not host one yet, so this page is the reference rather than an exercise: the problem, worked examples, and the solution in full. To type it out, the same problem runs in Python.
Where you start
public int TournamentRounds(int teams) {
}Worked examples
| Call | Result |
|---|---|
TournamentRounds(1) | 0 |
TournamentRounds(2) | 1 |
TournamentRounds(4) | 2 |
TournamentRounds(5) | 3 |
Hint
Repeatedly halve (rounding up) and count until one remains.
Reference solution in C#
public int TournamentRounds(int teams) {
if (teams <= 1) return 0;
int rounds = 0, t = teams;
while (t > 1) { t = (t + 1) / 2; rounds++; }
return rounds;
}