Detailed explanation of the basics of PHP doubly linked list

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 ); ?>

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"