php 数据结构之链表队列

php 链表队列

实例代码：

private $last;
private $first;
private $oldfirst;
private static $n=0;

public function __construct(){
$this->last = null;
$this->first = null;
$this->oldfirst = null;
}

public function push($item){
$this->oldfirst = $this->last;
$this->last = new Node();
$this->last->item = $item;
$this->last->next = null;
if(empty($this->first)){
$this->first = $this->last;
}else{
$this->oldfirst->next = $this->last;
}
self::$n++;
}

public function pop(){
if(self::$n<0){
return null;
}
$item = $this->first->item;
$this->first = $this->first->next;
self::$n--;
return $item;
}

}

class Node{
public $item;
public $next;
}

$Queue = new Queue();
$Queue->push("a");
$Queue->push("b");
$Queue->push("c");
echo $Queue->pop().PHP_EOL;
echo $Queue->pop().PHP_EOL;
echo $Queue->pop().PHP_EOL;
echo $Queue->pop().PHP_EOL;

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