I am trying to expand and improve the round-robin algorithm from 1v1 group to a 1v1v1v1 group(something like free for all). I've made the function itself to do the schedule, but when I tried to expand it, some teams repetead. For example, I have 16 teams and I want to have 5 rounds, team 1 appears 7 times in 5 rounds and team2 appears 3 times in 5 rounds. I need them to appear 5 times at most.I really can't understand how I can do it. Any advice is welcomed and links.
function make_schedule(array $teams, int $rounds = null, bool $shuffle = true, int $seed = null): array
{
$teamCount = count($teams);
if($teamCount < 4) {
return [];
}
//Account for odd number of teams by adding a bye
if($teamCount % 2 === 1) {
array_push($teams, null);
$teamCount += 1;
}
if($shuffle) {
//Seed shuffle with random_int for better randomness if seed is null
srand($seed ?? random_int(PHP_INT_MIN, PHP_INT_MAX));
shuffle($teams);
} elseif(!is_null($seed)) {
//Generate friendly notice that seed is set but shuffle is set to false
trigger_error('Seed parameter has no effect when shuffle parameter is set to false');
}
$quadTeamCount = $teamCount / 4;
if($rounds === null) {
$rounds = $teamCount - 1;
}
$schedule = [];
for($round = 1; $round <= $rounds; $round += 1) {
$matchupPrev = null;
foreach($teams as $key => $team) {
if($key >= $quadTeamCount ) {
break;
}
$keyCount = $key + $quadTeamCount;
$keyCount2 = $key + $quadTeamCount + 1;
$keyCount3 = $key + $quadTeamCount + 2;
$team1 = $team;
$team2 = $teams[$keyCount];
$team3 = $teams[$keyCount2];
$team4 = $teams[$keyCount3];
//echo "<pre>Round #{$round}: {$team1} - {$team2} - {$team3} - {$team4} == KeyCount: {$keyCount} == KeyCount2: {$keyCount2} == KeyCount3: {$keyCount3}</pre>";
//Home-away swapping
$matchup = $round % 2 === 0 ? [$team1, $team2, $team3, $team4 ] : [$team2, $team1, $team4, $team3];
$schedule[$round][] = $matchup ;
}
rotate($teams);
}
return $schedule;
}
Rotate function:
function rotate(array &$items)
{
$itemCount = count($items);
if($itemCount < 3) {
return;
}
$lastIndex = $itemCount - 1;
/**
* Though not technically part of the round-robin algorithm, odd-even
* factor differentiation included to have intuitive behavior for arrays
* with an odd number of elements
*/
$factor = (int) ($itemCount % 2 === 0 ? $itemCount / 2 : ($itemCount / 2) + 1);
$topRightIndex = $factor - 1;
$topRightItem = $items[$topRightIndex];
$bottomLeftIndex = $factor;
$bottomLeftItem = $items[$bottomLeftIndex];
for($i = $topRightIndex; $i > 0; $i -= 1) {
$items[$i] = $items[$i - 1];
}
for($i = $bottomLeftIndex; $i < $lastIndex; $i += 1) {
$items[$i] = $items[$i + 1];
}
$items[1] = $bottomLeftItem;
$items[$lastIndex] = $topRightItem;
}
For example:
If I set rounds to 5, every team play 5 matches. Array example Screenshot
Dealing with the 5th round:
Well, after I thought for a bit, maybe there isn't a way for them to play without repeatence, but if it is lowered to minumum, like every team should play 5 times only - this means once a round. That's what I meant. And what I meant under 'they repeat' is that there are like: 16 teams, 5 rounds and some teams are going like 7 times for all these rounds and other teams are going 3 times for these 5 rounds. I want to avoid this and to make every team play 5 rounds at most.