I have a code to generate bracket sheets for a tournament. I have players and each player is associated with an school. I need to sort an array with the players so there no first matches of players of the same school (or the lower same-school matches possible).
Something like this:
$players = array(
array('name' => 'juan', 'school' => 'ABC'), // 0
array('name' => 'leo', 'school' => 'ABC'), // 1
array('name' => 'arnold', 'school' => 'DEF'), // 2
array('name' => 'simon', 'school' => 'DEF'), // 3
array('name' => 'luke', 'school' => 'ECD'), // 4
array('name' => 'ash', 'school' => 'ECD'), // 5
);
// code to sort here
array_chunk($players, 2); // this generate an array with groups of two for matches.
In the above example [0] and [1] cant go together because they are on the same school. [0] can go with 3, for example.
I'm trying with usort, but I'm not sure what's the right way to approach this.
Ok, a new answer having re-examined the issue. The algorithm, I think, should be thus:
Implementation-wise, I found it easier to maintain 2 indexes - one of schools and 1 of players. I bundled it into a couple of classes because the inherently referential nature of objects makes life easier. My code is below... it works out of the box but may need some tweaking.
<?php
class School {
protected $name;
protected $players = [];
public function __construct($name) {
$this->name = $name;
}
public function get_name() {
return $this->name;
}
public function add_player($name) {
$this->players[] = $name;
}
public function del_player($name) {
if (($index = array_search($name, $this->players)) !== false) {
unset($this->players[$index]);
}
}
public function player_count() {
return count($this->players);
}
public function get_player() {
if (!reset($this->players)) {
return false;
}
return [
'school' => $this->name,
'name' => reset($this->players),
];
}
}
class Players {
protected $schools_index = [];
protected $player_index = [];
public function add_player($school, $player) {
// Create school if not exists
if (!isset($this->schools_index[$school])) {
$this->schools_index[$school] = new School($school);
}
// Add player to school and own index
$this->schools_index[$school]->add_player($player);
$this->player_index[$player] = $school;
}
public function del_player($school, $player) {
// From school index
$this->schools_index[$school]->del_player($player);
// From own index
if (isset($this->player_index[$player])) {
unset($this->player_index[$player]);
}
}
public function biggest_school($exclude = null) {
$rtn = null;
// Find school excluding the exclude. Don't get schools with nobody left in them.
foreach ($this->schools_index as $name=>$school) {
if ((!$exclude || $name != $exclude) && ($school->player_count()) && (!$rtn || $rtn->player_count() < $school->player_count())) {
$rtn = $school;
}
}
// If we didn't get a school, shitcan the exclude and try the excluded school
if (!$rtn && $exclude) {
if ($this->schools_index[$exclude]->player_count()) {
$rtn = $this->schools_index[$exclude];
}
}
return $rtn;
}
public function get_player() {
if (!reset($this->player_index)) {
return false;
}
return [
'school' => reset($this->player_index),
'name' => key($this->player_index),
];
}
public static function from_players_arr(array $players) {
$obj = new static();
foreach ($players as $player) {
// Add to indexes
$obj->add_player($player['school'], $player['name']);
}
return $obj;
}
}
$players = array(
array('name' => 'juan', 'school' => 'ABC'),
array('name' => 'leo', 'school' => 'ABC'),
array('name' => 'arnold', 'school' => 'ABC'),
array('name' => 'simon', 'school' => 'ABC'),
array('name' => 'luke', 'school' => 'ABC'),
array('name' => 'alan', 'school' => 'JKL'),
array('name' => 'jeff', 'school' => 'BAR'),
array('name' => 'paul', 'school' => 'FOO'),
);
$players_obj = Players::from_players_arr($players);
$pairs = [];
while ($player = $players_obj->get_player()) {
$players_obj->del_player($player['school'], $player['name']);
$opponent = $players_obj->biggest_school($player['school'])->get_player();
$pairs[] = [
$player['name'],
$opponent['name'],
];
$players_obj->del_player($opponent['school'], $opponent['name']);
}
var_dump($pairs);
Output is below:
array(4) {
[0] =>
array(2) {
[0] =>
string(4) "juan"
[1] =>
string(4) "alan"
}
[1] =>
array(2) {
[0] =>
string(3) "leo"
[1] =>
string(4) "jeff"
}
[2] =>
array(2) {
[0] =>
string(6) "arnold"
[1] =>
string(4) "paul"
}
[3] =>
array(2) {
[0] =>
string(5) "simon"
[1] =>
string(4) "luke"
}
}
What we are going to do, is split the players in 2 groups: contenders 1 & contenders 2. We're going to fill contenders a with consecutive players of the same school:
If we name the schools a single letter for brevity, what we'll essentially have is:
A A A A B B B C
C C D D E E F F
Or, if we flip it, it becomes clearer:
A C
A C
A D
A D
B E
B E
B F
C F
What happens if one school has > the half of the total number of players? Well, let's see:
A A A A A
A B B C D
So:
A A <= one A vs. A, which is unavoidable, but the method still works.
A B
A B
A C
A D
I cheated a bit here: I sorted out the players from the biggest school first. It however still works as long as we group schools together. Let's take my output of $a = range('A','F'); shuffle($a):, which here resulted in: FCADBE, which gives us:
F A
F D
C D
C B
C B
A B
A E
A E
.. which works, also for A > half:
C A
A A <= that one double again, unavoidable
A D
A B
A B
Let's break this into parts. What we have to do is:
The advantage of cutting it down is so you can find answers:
So, let's do that:
//sort by school
$players = ... your array ...
usort($players,function($playerA, $playerB){
return strcmp($playerA['school'], $playerB['school']);
});
//voila, sorted
//break this into 2 groups:
$size = ceil(count($players) / 2); // round UP
$groupA = array_slice($players,0,$size);
$groupB = array_slice($players,$size);
//create our duels array:
$duels = array_map(null, $groupA, $groupB);
$duels now has this content with your input:
[
[
{
"name": "juan",
"school": "ABC"
},
{
"name": "arnold",
"school": "DEF"
}
],
[
{
"name": "leo",
"school": "ABC"
},
{
"name": "ash",
"school": "ECD"
}
],
[
{
"name": "simon",
"school": "DEF"
},
{
"name": "luke",
"school": "ECD"
}
]
]