本文实例讲述了PHP双向链表定义与用法。分享给大家供大家参考，具体如下：

由于需要对一组数据多次进行移动操作，所以写个双向链表。但对php实在不熟悉，虽然测试各个方法没啥问题，就是不知道php语言深层的这些指针和unset有什么注意的地方，贴出来让大家教育吧。效率没测试....求谅解～

/**

* **双向链表

* @author zhiyuan12@

*/

/**

* 链表元素结点类

*/

class Node_Element {

public $pre = NULL; // 前驱

public $next = NULL; // 后继

public $key = NULL; // 元素键值

public $data = NULL; // 结点值

function __Construct($key, $data) {

$this->key = $key;

$this->data = $data;

}

}

/**

* 双向链表类

*/

class DoubleLinkedList {

private $head; // 头指针

private $tail; // 尾指针

private $current; // 当前指针

private $len; // 链表长度

function __Construct() {

$this->head = self::_getNode ( null, null );

$this->curelement = $this->head;

$this->tail = $this->head;

$len = 0;

}

/**

* @ desc: 读取链表全部结点

*/

public function readAll() {

$tmp = $this->head;

while ( $tmp->next !== null ) {

$tmp = $tmp->next;

var_dump ( $tmp->key, $tmp->data );

}

}

public function move($pos1, $pos2) {

$pos1Node = $this->findPosition ( $pos1 );

$pos2Node = $this->findPosition ( $pos2 );

if ($pos1Node !== null && $pos2Node !== null) {

$tmpKey = $pos1Node->key;

$tmpData = $pos1Node->data;

$pos1Node->key = $pos2Node->key;

$pos1Node->data = $pos2Node->data;

$pos2Node->key = $tmpKey;

$pos2Node->data = $tmpData;

return true;

}

return false;

}

/**

* @ desc: 在指定关键词删除结点

*

* @param : $key

* 指定位置的链表元素key

*/

public function delete($key) {

$pos = $this->find ( $key );

if ($pos !== null) {

$tmp = $pos;

$last = null;

$first = true;

while ( $tmp->next !== null && $tmp->next->key === $key ) {

$tmp = $tmp->next;

if (! $first) {

$this->delNode ( $last );

} else {

$first = false;

}

$last = $tmp;

}

if ($tmp->next !== null) {

$pos->pre->next = $tmp->next;

$tmp->next->pre = $pos->pre;

} else {

$pos->pre->next = null;

}

$this->delNode ( $pos );

$this->delNode ( $tmp );

}

}

/**

* @ desc: 在指定位置删除结点

*

* @param : $key

* 指定位置的链表元素key

*/

public function deletePosition($pos) {

$tmp = $this->findPosition ( $pos );

if ($tmp === null) {

return true;

}

if ($tmp === $this->getTail ()) {

$tmp->pre->next = null;

$this->delNode ( $tmp );

return true;

}

$tmp->pre->next = $tmp->next;

$tmp->next->pre = $tmp->pre;

$this->delNode ( $tmp );

}

/**

* @ desc: 在指定键值之前插入结点

*

* @param : $key

* //指定位置的链表元素key

* @param : $data

* //要插入的链表元素数据

* @param : $flag

* //是否顺序查找位置进行插入

*/

public function insert($key, $data, $flag = true) {

$newNode = self::_getNode ( $key, $data );

$tmp = $this->find ( $key, $flag );

if ($tmp !== null) {

$newNode->pre = $tmp->pre;

$newNode->next = $tmp;

$tmp->pre = $newNode;

$newNode->pre->next = $newNode;

} else {

$newNode->pre = $this->tail;

$this->tail->next = $newNode;

$this->tail = $newNode;

}

$this->len ++;

}

/**

* @ desc: 在指定位置之前插入结点

*

* @param : $pos

* 指定插入链表的位置

* @param : $key

* 指定位置的链表元素key

* @param : $data

* 要插入的链表元素数据

*/

public function insertPosition($pos, $key, $data) {

$newNode = self::_getNode ( $key, $data );

$tmp = $this->findPosition ( $pos );

if ($tmp !== null) {

$newNode->pre = $tmp->pre;

$newNode->next = $tmp;

$tmp->pre = $newNode;

$newNode->pre->next = $newNode;

} else {

$newNode->pre = $this->tail;

$this->tail->next = $newNode;

$this->tail = $newNode;

}

$this->len ++;

return true;

}

/**

* @ desc: 根据key值查询指定位置数据

*

* @param : $key

* //指定位置的链表元素key

* @param : $flag

* //是否顺序查找

*/

public function find($key, $flag = true) {

if ($flag) {

$tmp = $this->head;

while ( $tmp->next !== null ) {

$tmp = $tmp->next;

if ($tmp->key === $key) {

return $tmp;

}

}

} else {

$tmp = $this->getTail ();

while ( $tmp->pre !== null ) {

if ($tmp->key === $key) {

return $tmp;

}

$tmp = $tmp->pre;

}

}

return null;

}

/**

* @ desc: 根据位置查询指定位置数据

*

* @param : $pos

* //指定位置的链表元素key

*/

public function findPosition($pos) {

if ($pos <= 0 || $pos > $this->len)

return null;

if ($pos < ($this->len / 2 + 1)) {

$tmp = $this->head;

$count = 0;

while ( $tmp->next !== null ) {

$tmp = $tmp->next;

$count ++;

if ($count === $pos) {

return $tmp;

}

}

} else {

$tmp = $this->tail;

$pos = $this->len - $pos + 1;

$count = 1;

while ( $tmp->pre !== null ) {

if ($count === $pos) {

return $tmp;

}

$tmp = $tmp->pre;

$count ++;

}

}

return null;

}

/**

* @ desc: 返回链表头节点

*/

public function getHead() {

return $this->head->next;

}

/**

* @ desc: 返回链表尾节点

*/

public function getTail() {

return $this->tail;

}

/**

* @ desc: 查询链表节点个数

*/

public function getLength() {

return $this->len;

}

private static function _getNode($key, $data) {

$newNode = new Node_Element ( $key, $data );

if ($newNode === null) {

echo "new node fail!";

}

return $newNode;

}

private function delNode($node) {

unset ( $node );

$this->len --;

}

}

$myList = new DoubleLinkedList ();

$myList->insert ( 1, "test1" );

$myList->insert ( 2, "test2" );

$myList->insert ( "2b", "test2-b" );

$myList->insert ( 2, "test2-c" );

$myList->insert ( 3, "test3" );

$myList->insertPosition ( 5, "t", "testt" );

$myList->readAll ();

echo "+++";

$myList->deletePosition(0);

$myList->readAll ();

echo "..." . $myList->getLength ();

var_dump ( $myList->findPosition ( 3 )->data );

?>

运行结果：

int(1)

string(5) "test1"

int(2)

string(7) "test2-c"

int(2)

string(5) "test2"

string(2) "2b"

string(7) "test2-b"

string(1) "t"

string(5) "testt"

int(3)

string(5) "test3"

+++int(1)

string(5) "test1"

int(2)

string(7) "test2-c"

int(2)

string(5) "test2"

string(2) "2b"

string(7) "test2-b"

string(1) "t"

string(5) "testt"

int(3)

string(5) "test3"

...6string(5) "test2"

希望本文所述对大家PHP程序设计有所帮助。