二叉堆 binary heap 优先队列

* autoload.php

 接上次的blog   =>   https://blog.csdn.net/fareast_mzh/article/details/82832668

<?php
$prefixList = ['stack\\dogcat', 'stack', 'Heap'];

array_walk($prefixList, function($prefix) {
    spl_autoload_register(function($class) use ($prefix) {
        $base_dir = __DIR__ . DIRECTORY_SEPARATOR. str_replace('\\', '/', $prefix);
        $len = strlen($prefix);
        if (strncmp($prefix, $class, $len) !== 0) {
            return;
        }
        $relative_class = substr($class, $len);
        $file = $base_dir . str_replace('\\', '/', $relative_class) . '.php';
        if (!file_exists($file)) {
            throw new InvalidArgumentException($file.' does not exist');
        }
        require $file;
    });
}, null);

* 目录结构

* Heap/BinHeap.php  [ONGOING]

<?php
/**
 * 完全二叉树的数组实现
 * ==============================
 *         A
 *       /   \
 *     B      C
 *    / \    / \
 *   D  E   F  G
 *  /\  /
 * H I  J
 * ===============================
 * _ A B C D E F G H I J   _  _  _
 * 0 1 2 3 4 5 6 7 8 9 10 11 12 13
 */
namespace Heap;

class BinHeap {
    /** @var  int */
    protected $capacity;

    /** @var  int */
    protected $size;

    /** @var \SplFixedArray */
    protected $elements;

    const MIN_PQSIZE = 4;
    const MIN_DATA = null;

    public function __construct(int $maxElements) {
        if ($maxElements < self::MIN_PQSIZE) {
            throw new \AssertionError("Priority queue size is too small");
        }
        $this->elements = new \SplFixedArray($maxElements + 1);
        $this->capacity = $maxElements;
        $this->size = 0;
        /* dumb position 0 */
        $this->elements[0] = self::MIN_DATA;
    }

    public function isFull() {
        return $this->size >= $this->capacity;
    }

    public function insert($x) {
        if ($this->isFull()) {
            throw new \RuntimeException("Priority queue is full");
        }
        for ($i = ++$this->size; $this->elements[$i>>1] > $x; $i >>= 1) {
            $this->elements[$i] = $this->elements[ $i>>1 ];
        }
        $this->elements[ $i ] = $x;
    }

    public function isEmpty() {
        return $this->size === 0;
    }

    public function deleteMin() {
        if ($this->isEmpty()) {
            // throw new \RuntimeException("Priority queue is empty");
            return $this->elements[0];
        }
        $minElement = $this->elements[1];
        $lastElement = $this->elements[$this->size--];

        for ($i = 1; $i * 2 <= $this->size; $i = $child) {
            /* find smaller child */
            $child = $i * 2;
            if ($child !== $this->size && $this->elements[$child+1]
                < $this->elements[$child]) {
                $child++;
            }
            /* Percolate one level */
            if ($lastElement > $this->elements[$child]) {
                $this->elements[$i] = $this->elements[$child];
            } else {
                break;
            }
        }
        $this->elements[$i] = $lastElement;
        return $minElement;
    }
}

* index2.php

<?php

include './autoload.php';

use Heap\BinHeap;

$heap = new BinHeap(14);
var_dump($heap);