删除循环双向链表的所有节点需要遍历链表,将每个节点一一删除。它需要创建一个指向头的下一个节点的当前节点。删除当前节点并使用临时节点移动到下一个节点。重复这个过程,直到当前节点成为头节点。最后,删除头部。
函数deleteAllNodes就是为此目的而创建的。这是一个3步过程。
public function deleteAllNodes() {
if($this->head != null) {
//1.如果 head 不为空,则创建一个临时节点
//当前节点指向头的下一个
$temp = new Node();
$current = new Node();
$current = $this->head->next;
//2。如果当前节点不等于head,则删除
// 当前节点并使用 temp 将当前节点移动到下一个节点,
//重复该过程,直到电流到达头部
while($current != $this->head) {
$temp = $current->next;
$current = null;
$current = $temp;
}
//3。删除头部
$this->head = null;
}
echo "All nodes are deleted successfully.\n";
}
下面是一个完整的程序,它使用上面讨论的删除循环双向链表的所有节点的概念,这使得列表为空,大小为零。
<?php
//节点结构
class Node {
public $data;
public $next;
public $prev;
}
class LinkedList {
public $head;
public function __construct(){
$this->head = null;
}
//在列表末尾添加新元素
public function push_back($newElement) {
$newNode = new Node();
$newNode->data = $newElement;
$newNode->next = null;
$newNode->prev = null;
if($this->head == null) {
$this->head = $newNode;
$newNode->next = $this->head;
} else {
$temp = new Node();
$temp = $this->head;
while($temp->next !== $this->head) {
$temp = $temp->next;
}
$temp->next = $newNode;
$newNode->next = $this->head;
$newNode->prev = $temp;
$this->head->prev = $newNode;
}
}
//删除链表所有节点
public function deleteAllNodes() {
if($this->head != null) {
$temp = new Node();
$current = new Node();
$current = $this->head->next;
while($current != $this->head) {
$temp = $current->next;
$current = null;
$current = $temp;
}
$this->head = null;
}
echo "All nodes are deleted successfully.\n";
}
//显示列表内容
public function PrintList() {
$temp = new Node();
$temp = $this->head;
if($temp != null) {
echo "The list contains: ";
while(true) {
echo $temp->data." ";
$temp = $temp->next;
if($temp == $this->head)
break;
}
echo "\n";
} else {
echo "The list is empty.\n";
}
}
};
//测试代码
$MyList = new LinkedList();
//在列表中添加四个元素。
$MyList->push_back(10);
$MyList->push_back(20);
$MyList->push_back(30);
$MyList->push_back(40);
//显示列表内容。
$MyList->PrintList();
//删除链表所有节点
$MyList->deleteAllNodes();
//显示列表内容。
$MyList->PrintList();
?>
上面的代码将给出以下输出:
The list contains: 10 20 30 40
All nodes are deleted successfully.
The list is empty.