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    SplPriorityQueue::compare

    (PHP 5 >= 5.3.0, PHP 7)

    SplPriorityQueue::compare — Compare priorities in order to place elements correctly in the heap while sifting up

    Descrierea

    public SplPriorityQueue::compare ( mixed $priority1 , mixed $priority2 ) : int

    Compare priority1 with priority2.

    Parametri

    priority1

    The priority of the first node being compared.

    priority2

    The priority of the second node being compared.

    Valorile întoarse

    Result of the comparison, positive integer if priority1 is greater than priority2, 0 if they are equal, negative integer otherwise.

    Notă:

    Multiple elements with the same priority will get dequeued in no particular order.

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    User Contributed Notes 2 notes

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    16
    Anonymous
    15 years ago
    At this time, the documentation sais "Note: Multiple elements with the same priority will get dequeued in no particular order."

    If you need elements of equal priority to maintain insertion order, you can use something like:

    <?php

    class StablePriorityQueue extends SplPriorityQueue {
        protected     $serial = PHP_INT_MAX;
        public function     insert($value, $priority) {
                parent::insert($value, array($priority, $this->serial--));
        }
    }

    ?>
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    0
    Anonymous
    1 year ago
    To create a min-heap priority queue, and have extract() give you the lowest priority:

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