PHP實作雙向鍊錶的一例程式碼

/**
 * **雙向鍊錶
 * @author zhiyuan12@
 * @modified 2012-10-25
 * @site: bbs.it-home.org
*/
/**
 * 鍊錶元素結點類別
*/
class Node_Element {
 public $pre = NULL; // 前驅
 public $next = NULL; // 後繼
 public $key = NULL; // 元素鍵值
 public $data = NULL; // 結點值
 function __Construct($key, $data) {
 $this->key = $key;
 $this->data = $data;
 }
}
/**
 * 雙向鍊錶類別
*/
class DoubleLinkedList {
 private $head; // 頭指標
 private $tail; // 尾指標
 private $current; // 目前指標
 private $ // 鍊錶長度
 function __Construct() {
 $this->head = self::_getNode ( null, null );
 $this->curelement = $this->head;
 $ this->tail = $this->head;
 $len = 0;
 }
 /**
 * @ desc: 讀取鍊錶全部結點
*/
 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: 在指定關鍵字刪除結點
 *
 * @param : $key
 * 指定位置的鍊錶元素key
*/
 public function delete($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: 在指定位置刪除結點
 *
 * @param : $key
 * 指定位置的鍊錶元素key
*/
 public function deletePosition($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: 在指定鍵值之前插入結點
 *
 * @param : $key
 * //指定位置的鍊錶元素key
 * @param : $data  * //要插入的鍊錶元素資料
 * @param : $flag
 * //是否順序查找位置進行插入
*/
 public function insert($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結點
 *
 * @param : $pos
 * 指定插入鍊錶的位置
 * @param : $key
 * 指定位置的鍊錶元素key
 * @param : $data
 * 要插入的鍊錶元素資料
*/
 public function insertPosition($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 ++;
回傳true;
 }
 /**
 * @ desc: 根據key值查詢指定位置資料
 *
 * @param : $key
 * //指定位置的鍊錶元素key
 * @param : $flag
 * //是否順序查找
*/
 public function find($key, $flag = true) {
 if ($flag) {
 $ tmp = $this->頭;
 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;
 }
 }
 回傳 null;
 }
 /**
 * @ desc: 根據位置查詢指定位置資料
 *
 * @param : $pos
 * //指定位置的鍊錶元素key
*/
 public function findPosition($pos) {
 if ($pos  $this->len)
 返回null；
 if ($pos 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 ++;
 }
 }
 回傳 null;
 }
 /**
 * @ desc: 返回鍊錶頭節點
*/
 public function getHead() {
 return $this->head->next ;
 }
 /**
 * @ desc: 返回鍊錶尾節點
*/
 public function getTail() {
 return $this->tail;
 }
 /**
 * @ desc: 查詢鍊錶節點個數
*/
 public function getLength() {
 return $this->len;
 }
 真空負極函數 _getNode($key, $data) {
 $newNode = new Node_Element ( $key, $data );
 if ($newNode === null) {
 echo "新節點失敗！";
 }
 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();
//回顯“...”。
// var_dump ( $myList->findPosition ( 3 )->data );
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