Grouping N person randomly but evenly? (Name & Gender) - php

Question

So, I tried to create an algorithm(?) to assign a person to a classroom. The requirement for each class is :
Have at least 30 people and maximum of 45
The person name will not be "Homogen" (e.g: class 1 - 3 has all person name started with the letter "A", while class 4-5 the letter "B" etc.)
The gender is also evenly distributed
If the class is full, the remaining person will be moved to waiting list
My data has the column Unique ID, Name, and Gender. I'm still new to this kind of stuff (Algorithm?) so I don't even know where to start. Is it even possible? Where do I start? I am using PHP and my data is in MySQL Database

Answer 1

Step 1
You need to get data from DateBase (all people)
$host = '***';
$user = '***'';
$password = '***'';
$database = '***'';
$link = mysqli_connect($host, $user, $password, $database) or die("Error" . mysqli_error($link));
$query = "SELECT * FROM people";
$people = mysqli_query($link, $query) or die("Error" . mysqli_error($link));
mysqli_close($link);
Step 2
Conver mysql_result to Array and shuffle it.
$people = [];
foreach ($result as $person) {
$people[] = $person;
}
shuffle($people);
Step 3
There is algorithm:
$count = count($people);
// Classes
$classes = [];
const MIN_SIZE = 30;
const MAX_SIZE = 45;
$maxSizeClass= $count / MIN_SIZE;
$minSizeClass= $count / MAX_SIZE;
$countClasses = max(ceil($minSizeClass), floor($maxSizeClass));
$currentCountClass = $count / $countClasses;
$tmpClass = [];
foreach ($people as $person) {
if (count($tmpClass) < $currentCountClass) {
$tmpClass[] = $person;
} else {
$classes[] = $tmpClass;
$tmpClass = [];
}
}
if (count($tmpClass) >= MIN_SIZE) {
$classes[] = $tmpClass;
$tmpClass = [];
}
foreach ($tmpClass as $index => $person) {
foreach ($classes as &$class) {
if (count($class) < MAX_SIZE) {
$class[] = $person;
// be careful, PHP7 is OK
unset($tmpClass[$index]);
continue 2;
}
}
}
// persons awaiting distribution
$waitingQueue = $tmpClass;
Step 4
Result is:
$waitingQueue - persons awaiting distribution
$classes - classes with persons

Answer 2

$letters = array('a','b',....,'y','z');
foreach($letters as $letter){
$sql['male'] = "SELECT * FROM people_table WHERE person_name LIKE '".$letter."%' AND person_gender = 'male' ORDER BY person_name";
$sql['female'] = "SELECT * FROM people_table WHERE person_name LIKE '".$letter."%' AND person_gender = 'female' ORDER BY person_name";
foreach($sql as $key => $query){
$results[$key] = $connection->query($query);
for($i = 0; $i < $results[$key]->num_rows; $i++){
$people[$letter][$key][] = results->fetch_array(MYSQLI_ASSOC);
}
}
}
Here we have the lists of people listed by gender by letter... Now we can loop it and insert a man and a woman by pairs. If the count(); of the list of pairs is lesser than 30, people wait more. If bigger than 44 (because in pair isn't possible to have 45 people, if I don't missunderstand the question, of course) then save this 44 in a class array $class[$letter] which you can see all classes by each letter. To know about how many classes you have in total, you can use count($class); or if you would like to know how many classes of a specific letter you can do count($class[$letter]);.
You can redo other foreach in the $letters array or just put the loop inside the foreachabove to create the array of classes.
Inside the foreach($letters as $letter){} at the final:
if( !(count($people[$letter][$key]) < 15 OR count($people[$letter][$key]) < 15) ){
$she = count($people[$letter]['female'];
$he = count($people[$letter]['male'];
if($she < $he){
for($i = 0; $i < 2*count($she); $i++){
$class[$letter][$i] = $people[$letter]['female'][$i];
$class[$letter][$i+1] = $people[$letter]['male'][$i];
$i++;//Important to avoid replace values!
}
} else {
for($i = 0; $i < 2*count($he); $i++){
$class[$letter][$i] = $people[$letter]['female'][$i];
$class[$letter][$i+1] = $people[$letter]['male'][$i];
$i++;//Important to avoid replace values!
}
}
A false boolean in the bigger if means cannot create a class with this letter gender evenly distributed. You can loop again to make each class in an entry of an array.