NAME

SkewHeap - mergable priority queues

SYNOPSIS

use sysread\SkewHeap\SkewHeap;

$heap = new SkewHeap;

foreach ($tasks as $task) {
    $heap->put($task);
}

while (!$heap->is_empty()) {
    my $next_task = $heap->take();
    do_stuff_to($next_task);
}

DESCRIPTION

A skew heaps are light-weight priority queues notable for their ability to be quickly merged with other heaps.

INSTALLATION

composer require sysread/php-skewheap

USAGE

CONSTRUCTOR

Accepts an optional argument specifying a function to be used when comparing entries in the heap that returns -1, 0, or 1 if the first entry has a higher, equal, or lower priority, respectively. If not specified or null, a simple numeric comparison is used, giving higher priority to the lower value.

Any number of source heaps from which the skew heap should be initially populated may be passed as additional arguments to the constructor.

$heap = new SkewHeap;

$heap = new SkewHeap(function($a, $b) {
    return $a - $b;
});

$heap = new SkewHeap(null, $heap1, $heap2, ...);

METHODS

size()

Returns the number of items in the heap.

is_empty()

Returns true if there is at least one item in the queue.

put(...$items)

Inserts any number of items into the queue. Returns the new queue size.

peek()

Returns the top item in the queue without removing it. Returns null when the queue is empty.

take()

Removes and returns the next item in the queue. Returns null if the queue is empty.

drain()

Removes and returns an array of all items in the queue.

explain()

Prints out a visual explanation of the heap structure for debugging.

AUTHOR

Jeff Ober sysread@fastmail.fm

LICENSE

Copyright (c) 2020 Jeff Ober

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.