双向链表

class Node{
 	public $data=null;
 	public $next = null;
 	public $prev=null;
 	public function __construct($data=null){
 		$this->data = $data;
 	}
 }
class BubbleList{
	public $header;
	public function __construct($data=null){
		$this->header = new Node();
	}
	//插入
	public function insert($data){
		$current = $this->header;
		while($current->next){
			$current=$current->next;
		}
		$Node = new Node($data);
		$current->next = $Node;//新节点绑定于前节点
		$Node->prev=$current;//新节点存储于前节点
	}
	//遍历
	public function Link(){
		$current=$this->header;
		while($current){
			echo $current->data;
			echo "\r\n";
			$current=$current->next;
		}
	}
	//通过数字返回所在位置
	public function find($num){
		$current = $this->header;
		$index=1;
		while($index <= $num){
			$current=$current->next;
			$index++;
		}
		return $current;
	}
	//修改所在位置数字
	public function update($num,$data){
		$current = $this->header;
		$index=1;
		while($index <= $num){
			$index++;
			$current = $current->next;
		}

		$current->data = $data;
	}
	//固定位置插入数字
	public function addData($num,$data){
		$current = $this->header;
		$index=1;
		while($index <= $num){
			$prev = $current;
			$index++;
			$current=$current->next;
		}	
		$pNode = new Node($data);

		$pNode->next = $current;
		$pNode->prev = $prev;

		$prev->next=$pNode;
		$current->prev = $pNode;
	}	
	//通过固定位置删除
	public function del($num){
		$current = $this->header;
		$index=1;
		while($index <= $num){
			$prev = $current;
			$index++;
			$current = $current->next;
		}
		$next = $current->next;
		$prev->next = $next;
		$next->prev = $prev;
	}
}

$obj = new BubbleList();
$arr=[100,3,90,1,40,5,4,100,8];
foreach ($arr as $key => $value) {
	$obj->insert($value);
}
// $obj->addData(4,7);
//$obj->del(5);
//$obj->find(3);
//$obj->update(3,89);
$obj->Link();