数据结构示例-删除循环链表的开头节点

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📜 数据结构示例-删除循环链表的开头节点

📅 最后修改于: 2020-10-15 06:01:58 🧑 作者: Mango

问：程序从循环链表的开头删除一个新节点。

说明

在此程序中，我们将创建一个循环链接列表，并从列表的开头删除一个节点。如果列表为空，则print消息“列表为空”。如果列表不为空，我们将使头部指向列表中的下一个节点，即，我们将删除第一个节点。

从头删除节点后的循环链表

在此，A代表列表的开头。我们需要从列表的开头删除一个节点。因此，我们将删除A，以使B成为新的头部，而尾部将指向新的头部。

算法

定义一个Node类，该类代表列表中的一个节点。它具有两个属性数据，下一个将指向下一个节点。
定义另一个用于创建循环链接列表的类，它具有两个节点：head和tail。它有两种方法：deleteStart()和display()。
deleteStart()将从列表的开头删除该节点：
1. 它首先检查head是否为空(空列表)，然后它将从函数返回，因为列表中没有节点。
2. 如果列表不为空，它将检查列表是否只有一个节点。
3. 如果列表只有一个节点，则它将head和tail都设置为null。
4. 如果列表中有多个节点，那么头部将指向列表中的下一个节点，也就是说，我们将删除前一个头部节点，而尾部将指向新的头部。
display()将显示列表中存在的所有节点。
1. 定义一个新节点“当前”，该节点将指向头部。
2. 打印current.data，直到current再次指向head。
3. 当前将在每次迭代中指向列表中的下一个节点。

示例：

Python

#Represents the node of list.
class Node:
    def __init__(self,data):
        self.data = data;
        self.next = None;
 
class CreateList:
    #Declaring head and tail pointer as null.
    def __init__(self):
        self.head = Node(None);
        self.tail = Node(None);
        self.head.next = self.tail;
        self.tail.next = self.head;
    
    #This function will add the new node at the end of the list.
    def add(self,data):
        newNode = Node(data);
        #Checks if the list is empty.
        if self.head.data is None:
            #If list is empty, both head and tail would point to new node.
            self.head = newNode;
            self.tail = newNode;
            newNode.next = self.head;
        else:
            #tail will point to new node.
            self.tail.next = newNode;
            #New node will become new tail.
            self.tail = newNode;
            #Since, it is circular linked list tail will point to head.
            self.tail.next = self.head;
    
    #Deletes node from the beginning of the list
    def deleteStart(self):
        #Checks whether list is empty
        if(self.head == None):
            return;
        else:
            #Checks whether contain only one element
            #If not, head will point to next element in the list and tail will point to new head.
            if(self.head != self.tail ):
                self.head = self.head.next;
                self.tail.next = self.head;
            #If the list contains only one element 
            #then it will remove it and both head and tail will point to null
            else:
                self.head = self.tail = None;
            
    #Displays all the nodes in the list
    def display(self):
        current = self.head;
        if self.head is None:
            print("List is empty");
            return;
        else:
            #Prints each node by incrementing pointer.
            print(current.data, end= ' ');
            while(current.next != self.head):
                current = current.next;
                print(current.data,end=' ');
            print("\n");
 
class CircularLinkedList:
    cl = CreateList();
    #Adds data to the list
    cl.add(1);
    cl.add(2);
    cl.add(3);
    cl.add(4);
    #Printing original list
    print("Original List:");
    cl.display();
    while(cl.head != None):
        cl.deleteStart();
        #Printing updated list
        print("Updated List:");
        cl.display();

输出：

Original List: 
 1 2 3 4
Updated List: 
 2 3 4
Updated List: 
 3 4
Updated List: 
 4
Updated List: 
List is empty

C

#include 
#include 
#include 
 
//Represents the node of list.
struct node{
    int data;
    struct node *next;
};
 
//Declaring head and tail pointer as null.
struct node *head = NULL;
struct node *tail = NULL;
 
//This function will add the new node at the end of the list.
void add(int data){
    //Create new node
    struct node *newNode = (struct node*)malloc(sizeof(struct node));
    newNode->data = data;
    //Checks if the list is empty.
    if(head == NULL){
        //If list is empty, both head and tail would point to new node.
        head = newNode;
        tail = newNode;
        newNode->next = head;
    }else {
        //tail will point to new node.
        tail->next = newNode;
        //New node will become new tail.
        tail = newNode;
        //Since, it is circular linked list tail will point to head.
        tail->next = head;
    }
}
 
//Deletes node from the beginning of the list
void deleteStart() {
    //Checks whether list is empty
    if(head == NULL) {
        return;
    }
    else {
        //Checks whether contain only one element
        //If not, head will point to next element in the list and tail will point to new head.
        if(head != tail ) {
            head = head->next;
            tail->next = head;
        }
        //If the list contains only one element 
        //then it will remove it and both head and tail will point to null
        else {
            head = tail = NULL;
        }
    }
}
    
//This function will display the nodes of circular linked list
void display(){
    struct node *current = head;
    if(head == NULL){
        printf("List is empty");
    }
    else{
         do{
             //Prints each node by incrementing pointer.
            printf("%d ", current->data);
            current = current->next;
        }while(current != head);
        printf("\n");
    }
}
    
int main()
{
   //Adds data to the list
   add(1);
   add(2);
   add(3);
   add(4);
   //Printing original list
   printf("Original List:\n ");
   display();
   while(head != NULL) {
       deleteStart();
       //Printing updated list
       printf("Updated List:\n ");
       display();
   }
   
   return 0;
}

输出：

Original List: 
 1 2 3 4
Updated List: 
 2 3 4
Updated List: 
 3 4
Updated List: 
 4
Updated List: 
List is empty

JAVA

public class DeleteStart {
    //Represents the node of list.
    public class Node{
        int data;
        Node next;
        public Node(int data) {
            this.data = data;
        }
    }
    
    //Declaring head and tail pointer as null.
    public Node head = null;
    public Node tail = null;
    
    //This function will add the new node at the end of the list.
    public void add(int data){
        //Create new node
        Node newNode = new Node(data);
        //Checks if the list is empty.
        if(head == null) {
             //If list is empty, both head and tail would point to new node.
            head = newNode;
            tail = newNode;
            newNode.next = head;
        }
        else {
            //tail will point to new node.
            tail.next = newNode;
            //New node will become new tail.
            tail = newNode;
            //Since, it is circular linked list tail will point to head.
            tail.next = head;
        }
    }
    
    //Deletes node from the beginning of the list
    public void deleteStart() {
        //Checks whether list is empty
        if(head == null) {
            return;
        }
        else {
            //Checks whether contain only one element
            //If not, head will point to next element in the list and tail will point to new head.
            if(head != tail ) {
                head = head.next;
                tail.next = head;
            }
            //If the list contains only one element 
            //then it will remove it and both head and tail will point to null
            else {
                head = tail = null;
            }
        }
    }
    
    //Displays all the nodes in the list
    public void display() {
        Node current = head;
        if(head == null) {
            System.out.println("List is empty");
        }
        else {
             do{
                //Prints each node by incrementing pointer.
                System.out.print(" "+ current.data);
                current = current.next;
            }while(current != head);
            System.out.println();
        }
    }
    
    public static void main(String[] args) {
        DeleteStart cl = new DeleteStart();
        //Adds data to the list
        cl.add(1);
        cl.add(2);
        cl.add(3);
        cl.add(4);
        //Printing original list
        System.out.println("Original List: ");
        cl.display();
        while(cl.head != null) {
            cl.deleteStart();
            //Printing updated list
            System.out.println("Updated List: ");
            cl.display();
        }
    }
}

输出：

Original List: 
 1 2 3 4
Updated List: 
 2 3 4
Updated List: 
 3 4
Updated List: 
 4
Updated List: 
List is empty

C＃

using System; 
namespace CircularLinkedList 
{                     
    public class Program
    {
        //Represents the node of list.
        public class Node{
            public T data;
            public Node next;
            public Node(T value) {
                data = value;
                next = null;
            }
        }
        
        public class CreateList{
            public Node head = null;             
             public Node tail = null;
            
            //This function will add the new node at the end of the list.
            public void add(T data){
                //Create new node
                Node newNode = new Node(data);
                //Checks if the list is empty.
                if(head == null){
                    head = newNode;
                    tail = newNode;
                    newNode.next = head;
                }else{
                    //tail will point to new node.
                    tail.next = newNode;
                    //New node will become new tail.
                    tail = newNode;
                    //Since, it is circular linked list tail will point to head.
                    tail.next = head;
                }
            }
            
            //Deletes node from the beginning of the list
            public void deleteStart() {
                //Checks whether list is empty
                if(head == null) {
                    return;
                }
                else {
                    //Checks whether contain only one element
                    //If not, head will point to next element in the list and tail will point to new head.
                    if(head != tail ) {
                        head = head.next;
                        tail.next = head;
                    }
                    //If the list contains only one element 
                    //then it will remove it and both head and tail will point to null
                    else {
                        head = tail = null;
                    }
                }
            }
            
            //Displays all the nodes in the list
            public void display(){
                Node current = head;
                if(head == null){
                    Console.WriteLine("List is empty");
                }
                else{
                    do{
                        //Prints each node by incrementing pointer.
                        Console.Write(" "+ current.data);
                        current = current.next;
                    }while(current != head);
                    Console.WriteLine();
                }
            }
        }
        
        public static void Main()
        {
            
        CreateList cl = new CreateList();
        //Adds data to the list
        cl.add(1);
        cl.add(2);
        cl.add(3);
        cl.add(4);
        //Printing original list
        Console.WriteLine("Original List: ");
        cl.display();
        while(cl.head != null) {
            cl.deleteStart();
            //Printing updated list
            Console.WriteLine("Updated List: ");
            cl.display();
        }
        }    
    }
}

输出：

Original List: 
 1 2 3 4
Updated List: 
 2 3 4
Updated List: 
 3 4
Updated List: 
 4
Updated List: 
List is empty

PHP：




data = $data;
        $this->next = NULL;
    }
}
class CreateList{
    //Declaring head and tail pointer as null.
    public $head;
    public $tail;
    function __construct(){
        $this->head = NULL;
        $this->tail = NULL;
    }
    //This function will add the new node at the end of the list.
    function add($data){
        //Create new node
        $newNode = new Node($data);
        //Checks if the list is empty.
        if($this->head == NULL){
            //If list is empty, both head and tail would point to new node.
            $this->head = $newNode;
            $this->tail = $newNode;
            $newNode->next = $this->head;
        }
        else{
            //tail will point to new node.
            $this->tail->next = $newNode;
            //New node will become new tail.
            $this->tail = $newNode;
            //Since, it is circular linked list tail will point to head.
            $this->tail->next = $this->head;
        }
    }
    
    //Deletes node from the beginning of the list
    function deleteStart() {
        //Checks whether list is empty
        if($this->head == NULL) {
            return;
        }
        else {
            //Checks whether contain only one element
            //If not head, will point to next element in the list and tail will point to new head.
            if($this->head != $this->tail ) {
                $this->head = $this->head->next;
                $this->tail->next = $this->head;
            }
            //If the list contains only one element 
            //then it will remove it and both head and tail will point to null
            else {
                $this->head = $this->tail = NULL;
            }
        }
    }
    
    //Displays all the nodes in the list
    function display() {
        $current = $this->head;
        if($this->head == NULL) {
            echo "List is empty";
        }
        else {
             do{
                //Prints each node by incrementing pointer.
                echo(" $current->data");
                $current = $current->next;
            }while($current != $this->head);
            echo "
";
        }
    }   
}
$cl = new CreateList();
//Adds data to the list
$cl->add(1);
$cl->add(2);
$cl->add(3);
$cl->add(4);
//Printing original list
echo "Original List:
";
$cl->display();
while($cl->head != NULL) {
    $cl->deleteStart();
    //Printing updated list
    echo "Updated List:
";
    $cl->display();
}
?>

输出：

Original List: 
 1 2 3 4
Updated List: 
 2 3 4
Updated List: 
 3 4
Updated List: 
 4
Updated List: 
List is empty