PHP 5.6.0 released

The SplPriorityQueue class

(PHP 5 >= 5.3.0)

Giriş

The SplPriorityQueue class provides the main functionalities of an prioritized queue, implemented using a max heap.

Sınıf Sözdizimi

SplPriorityQueue implements Iterator , Countable {
/* Yöntemler */
public __construct ( void )
public int compare ( mixed $priority1 , mixed $priority2 )
public int count ( void )
public mixed current ( void )
public mixed extract ( void )
public void insert ( mixed $value , mixed $priority )
public bool isEmpty ( void )
public mixed key ( void )
public void next ( void )
public void recoverFromCorruption ( void )
public void rewind ( void )
public void setExtractFlags ( int $flags )
public mixed top ( void )
public bool valid ( void )
}

İçindekiler

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User Contributed Notes 3 notes

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4
lsroudi at gmail dot com
6 months ago
<?php

/**
* Description of PriorityQueue
*
* (c) lsroudi http://lsroudi.com/ <lsroudi@gmail.com>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
interface PriorityLoggerInterface {

    public function
insert($value, $priority);
}

class
PriorityLogger extends SplPriorityQueue implements PriorityLoggerInterface {
   
}

class
Logger {

    const
ERROR = 3;
    const
NOTICE = 1;
    const
WARNING = 2;

    private
$priorityLogger;

    public function
__construct(PriorityLoggerInterface $priorityLogger)
    {
       
$this->priorityLogger = $priorityLogger;
    }

    public function
addMessage($value, $priority)
    {
       
$this->priorityLogger->insert($value, $priority);
    }

    public function
getPriorityLogger()
    {
        return
$this->priorityLogger;
    }

}

$priorityLogger = new PriorityLogger();

$logger = new Logger($priorityLogger);
$logger->addMessage('Message with notice type', Logger::NOTICE);
$logger->addMessage('Message with warning type', Logger::WARNING);
$logger->addMessage('Message with error type', Logger::ERROR);

$priorityLoggerQueue = $logger->getPriorityLogger();

foreach (
$priorityLoggerQueue as $queue){
    print
$queue . PHP_EOL;
}

//Résultat
//Message with error type
//Message with warning type
//Message with notice type
?>
up
6
rajatn at rediff dot co dot in
4 years ago
quick implementation of SPL Priority Queue:

<?php

class PQtest extends SplPriorityQueue
{
    public function
compare($priority1, $priority2)
    {
        if (
$priority1 === $priority2) return 0;
        return
$priority1 < $priority2 ? -1 : 1;
    }
}

$objPQ = new PQtest();

$objPQ->insert('A',3);
$objPQ->insert('B',6);
$objPQ->insert('C',1);
$objPQ->insert('D',2);

echo
"COUNT->".$objPQ->count()."<BR>";

//mode of extraction
$objPQ->setExtractFlags(PQtest::EXTR_BOTH);

//Go to TOP
$objPQ->top();

while(
$objPQ->valid()){
   
print_r($objPQ->current());
    echo
"<BR>";
   
$objPQ->next();
}

?>

output:

COUNT->4
Array ( [data] => B [priority] => 6 )
Array ( [data] => A [priority] => 3 )
Array ( [data] => D [priority] => 2 )
Array ( [data] => C [priority] => 1 )
up
0
Hayley Watson
3 months ago
For a heap-based priority queue to be at its most effective, the "priority" should be something that can take on a wide range of values (lengths, timestamps, populations). It optimises the tasks of searching the queue for the appropriate place to insert an item (and inserting it); and removing the first item in the list.

Items may potentially be inserted into the queue wherever two adjacent items have different priorities. The heap structure is an efficient way of indexing such insertion points when there are many of them distributed throughout the list.

If you have a sharply-limited enumeration of possible priority values, then there are very few insertion possible insertion points - one for each priority value. In that situation, one can make the insertion points explicit (and thus eliminate the need to maintain a heap indexing them) by implementing your priority queue as a list of simple queues from which you draw successive items from the highest-priority nonempty queue.
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