Detailed explanation of PHP's SplHeap heap

Heap is a data structure designed to implement priority queues. It is implemented by constructing a binary heap (a type of binary tree). The heap with the largest root node is called the maximum heap or large root heap, and the heap with the smallest root node is called the minimum heap or small root heap. Binary heaps are also commonly used for sorting (heap sort). SplHeap is an abstract class that implements the Iterator and Countable interfaces. The maximum heap (SplMaxHeap) and the minimum heap (SplMinHeap) are implemented by inheriting it and can be used directly in PHP programs.

Class summary:

abstract SplHeap implements Iterator , Countable {
    // 创建一个空堆
    public __construct ( void )
    // 比较两个节点的大小
    abstract protected int compare ( mixed $value1 , mixed $value2 )
    // 返回堆节点数
    public int count ( void )
    // 返回迭代指针指向的节点
    public mixed current ( void )
    // 从堆顶部提取一个节点并重建堆
    public mixed extract ( void )
    // 向堆中添加一个节点并重建堆
    public void insert ( mixed $value )
    // 判断是否为空堆
    public bool isEmpty ( void )
    // 返回迭代指针指向的节点的键
    public mixed key ( void )
    // 迭代指针指向下一节点
    public void next ( void )
    // 恢复堆
    public void recoverFromCorruption ( void )
    // 重置迭代指针
    public void rewind ( void )
    // 返回堆的顶部节点
    public mixed top ( void )
    // 判断迭代指针指向的节点是否存在
    public bool valid ( void )
}

Example description:

<?php
/**  
 * 实现一个自己的最大堆
 *  
 * @author 疯狂老司机
 */ 
class iMaxHeap extends SplHeap {
    /**
     * 实现compare抽象方法，使用关联数组的值进行比较排序
     * SplMaxHeap不能满足我们的需求
     */
    public function compare($array1, $array2) {
        $values1 = array_values($array1);
        $values2 = array_values($array2);
        if ($values1[0] === $values2[0]) return 0;
        return $values1[0] < $values2[0] ? -1 : 1;
    }
}

$heap = new iMaxHeap();
$heap->insert(array (&#39;a&#39; => 12));
$heap->insert(array (&#39;b&#39; => 20));
$heap->insert(array (&#39;c&#39; => 23));
$heap->insert(array (&#39;d&#39; => 32));
$heap->insert(array (&#39;e&#39; => 15));
$heap->insert(array (&#39;f&#39; => 17));
$heap->insert(array (&#39;g&#39; => 31));
$heap->insert(array (&#39;h&#39; => 11));
$heap->insert(array (&#39;i&#39; => 18));
$heap->insert(array (&#39;j&#39; => 24));

var_dump($heap->top());

while ($heap->valid()) {
    $cur = $heap->current();
    list ($team, $score) = each($cur);
    echo $team . &#39;: &#39; . $score . &#39;<br/>&#39;;
    $heap->next();
}
?>

The above output:

array (size=1)
'd' => int 32
d: 32
g: 31
j: 24
c: 23
b: 20
i: 18
f: 17
e: 15
a: 12
h: 11

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