PHP implementation of a two-way linked list of a sample code

/** * * * Double linked list * @author zhiyuan12@ * @modified 2012-10-25 * @site: bbs.it-home.org */ /** * Linked list element node class */ Class Node_element { Public $pre = NULL; Precursor Public $next = NULL; Subsequent Public $key = NULL; Element key value Public $data = NULL; Node value function __construct ($key, $data) { $this->key = $key; $this->data = $data; } } /** * Bidirectional linked List class */ Class Doublelinkedlist { Private $head; Head pointer Private $tail; Tail hands Private $current; Current pointer Private $len; Linked list length function __construct () { $this->head = Self::_getnode (null, NULL); $this->curelement = $this->head; $this->tail = $this->head; $len = 0; } /** * @ desc: Read all nodes of the list */ Public Function ReadAll () { $tmp = $this->head; while ($tmp->next!== null) { $tmp = $tmp->next; Var_dump ($tmp->key, $tmp->data); } } Public function Move ($pos 1, $pos 2) { $pos 1Node = $this->findposition ($pos 1); $pos 2Node = $this->findposition ($pos 2); if ($pos 1Node!== null && $pos 2Node!== null) { $tmpKey = $pos 1node->key; $tmpData = $pos 1node->data; $pos 1node->key = $pos 2node->key; $pos 1node->data = $pos 2node->data; $pos 2node->key = $tmpKey; $pos 2node->data = $tmpData; return true; } return false; } /** * @ desc: Delete node in specified keyword * * @param: $key * Specify the location of the linked list element key */ Public Function Delete ($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: Delete node at specified location * * @param: $key * Specify the location of the linked list element key */ Public Function Deleteposition ($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: Insert a node before specifying a key value * * @param: $key *//list element of the specified position key * @param: $data *//Linked list element data to be inserted * @param: $flag *//whether to insert in order to find location */ Public Function Insert ($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: Insert a node before the specified position * * @param: $pos * Specify where to insert the linked list * @param: $key * Specify the location of the linked list element key * @param: $data * The linked list element data to be inserted */ Public Function Insertposition ($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: Query specified location data based on key value * * @param: $key *//list element of the specified position key * @param: $flag *//whether to search sequentially */ Public function Find ($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: Specify location data based on location query * * @param: $pos *//list element of the specified position key */ Public Function Findposition ($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: Return to the list header node */ Public Function GetHead () { return $this->head->next; } /** * @ desc: Returns the link footer node */ Public Function GetTail () { return $this->tail; } /** * @ desc: Query the number of linked list nodes */ 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); ?> Copy Code

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