问. 双向链表删除头节点程序。

2025年03月17日 | 阅读 9 分钟

说明

在本程序中，我们将创建一个双向链表并从列表的开头删除一个节点。如果列表为空，则打印消息“列表为空”。如果列表不为空，我们将让头部指向列表中的下一个节点，然后；我们将删除第一个节点。

Program to delete a new node from the beginning of the doubly linked list

以上面的例子为例，new 是列表的头。让 head 指向列表中的下一个节点。现在，节点 1 将成为新的头节点，从而删除节点 new。

算法

定义一个 Node 类，它表示列表中的一个节点。它将有三个属性：数据、previous 指向前一个节点，以及 next 指向下一个节点。
定义另一个用于创建双向链表的类，它有两个节点：头节点和尾节点。最初，头节点和尾节点将指向 null。
deleteFromStart() 将从列表开头删除一个节点
1. 它首先检查 head 是否为 null（链表为空），然后，它将从函数返回，因为链表中没有节点。
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，它将 head 和 tail 都设置为 null。
4. 如果列表中有多个节点，则头部将指向列表中的下一个节点，并删除旧的头部节点。
display() 将显示列表中存在的所有节点。
1. 定义一个新节点“current”，它将指向头节点。
2. 打印 current.data 直到 current 指向 null。
3. 在每次迭代中，current 将指向列表中的下一个节点。

解决方案

Python

#Represent a node of doubly linked list
class Node:
    def __init__(self,data):
        self.data = data;
        self.previous = None;
        self.next = None;
        
class DeleteStart:
    #Represent the head and tail of the doubly linked list
    def __init__(self):
        self.head = None;
        self.tail = None;
        
    #addNode() will add a node to the list
    def addNode(self, data):
        #Create a new node
        newNode = Node(data);
        
        #If list is empty
        if(self.head == None):
            #Both head and tail will point to newNode
            self.head = self.tail = newNode;
            #head's previous will point to None
            self.head.previous = None;
            #tail's next will point to None, as it is the last node of the list
            self.tail.next = None;
        else:
            #newNode will be added after tail such that tail's next will point to newNode
            self.tail.next = newNode;
            #newNode's previous will point to tail
            newNode.previous = self.tail;
            #newNode will become new tail
            self.tail = newNode;
            #As it is last node, tail's next will point to None
            self.tail.next = None;
            
    #deleteFromStart() will delete a node from the beginning of the list
    def deleteFromStart(self):
        #Checks whether list is empty
        if(self.head == None):
            return;
        else:
            #Checks whether the list contains only one element
            if(self.head != self.tail):
                #head will point to next node in the list
                self.head = self.head.next;
                #Previous node to current head will be made None
                self.head.previous = None;
                
            #If the list contains only one element 
            #then, it will remove the node, and now both head and tail will point to None

            else:
                self.head = self.tail = None;
                
    #display() will print out the nodes of the list
    def display(self):
        #Node current will point to head
        current = self.head;
        if(self.head == None):
            print("List is empty");
            return;
        while(current != None):
            #Prints each node by incrementing pointer.
            print(current.data),
            current = current.next;
        print();
       
dList = DeleteStart();
#Add nodes to the list
dList.addNode(1);
dList.addNode(2);
dList.addNode(3);
dList.addNode(4);
dList.addNode(5);
 
#Printing original list
print("Original List: ");
dList.display();
while(dList.head != None):
    dList.deleteFromStart();
    #Printing updated list
    print("Updated List: ");
    dList.display();

输出

Original List: 
1 2 3 4 5 
Updated List: 
2 3 4 5 
Updated List: 
3 4 5 
Updated List: 
4 5 
Updated List: 
5 
Updated List: 
List is empty

C

#include <stdio.h>
 
//Represent a node of the doubly linked list

struct node{
    int data;
    struct node *previous;
    struct node *next;
};    
 
//Represent the head and tail of the doubly linked list
struct node *head, *tail = NULL;
 
//addNode() will add a node to the list
void addNode(int data) {
    //Create a new node
    struct node *newNode = (struct node*)malloc(sizeof(struct node));
    newNode->data = data;
    
    //If list is empty
    if(head == NULL) {
        //Both head and tail will point to newNode
        head = tail = newNode;
        //head's previous will point to NULL
        head->previous = NULL;
        //tail's next will point to NULL, as it is the last node of the list
        tail->next = NULL;
    }
    else {
        //newNode will be added after tail such that tail's next will point to newNode
        tail->next = newNode;
        //newNode's previous will point to tail
        newNode->previous = tail;
        //newNode will become new tail
        tail = newNode;
        //As it is last node, tail's next will point to NULL
        tail->next = NULL;
    }
}
 
//deleteFromStart() will delete a node from the beginning of the list
void deleteFromStart() {
    //Checks whether list is empty
    if(head == NULL) {
        return;
    }
    else {
        //Checks whether the list contains only one element
        if(head != tail) {
            //head will point to next node in the list
            head = head->next;
            //Previous node to current head will be made NULL
            head->previous = NULL;
        }
        //If the list contains only one element 
        //then, it will remove node and now both head and tail will point to NULL
        else {
            head = tail = NULL;
        }
    }
}
 
//display() will print out the nodes of the list
void display() {
    //Node current will point to head
    struct node *current = head;
    if(head == NULL) {
        printf("List is empty\n");
        return;
    }
    while(current != NULL) {
        //Prints each node by incrementing pointer.
        printf("%d ",current->data);
        current = current->next;
    }
    printf("\n");
}
    
int main()
{
    //Add nodes to the list
    addNode(1);
    addNode(2);
    addNode(3);
    addNode(4);
    addNode(5);
    
    //Printing original list
    printf("Original List: \n");
    display();
    while(head != NULL) {
        deleteFromStart();
        //Printing updated list
        printf("Updated List: \n");
        display();
    }    
 
    return 0;
}

输出

Original List: 
1 2 3 4 5 
Updated List: 
2 3 4 5 
Updated List: 
3 4 5 
Updated List: 
4 5 
Updated List: 
5 
Updated List: 
List is empty

JAVA

public class DeleteStart {
    
    //Represent a node of the doubly linked list

    class Node{
        int data;
        Node previous;
        Node next;
        
        public Node(int data) {
            this.data = data;
        }
    }
    
    //Represent the head and tail of the doubly linked list
    Node head, tail = null;
    
    //addNode() will add a node to the list
    public void addNode(int data) {
        //Create a new node
        Node newNode = new Node(data);
        
        //If list is empty
        if(head == null) {
            //Both head and tail will point to newNode
            head = tail = newNode;
            //head's previous will point to null
            head.previous = null;
            //tail's next will point to null, as it is the last node of the list
            tail.next = null;
        }
        else {
            //newNode will be added after tail such that tail's next will point to newNode
            tail.next = newNode;
            //newNode's previous will point to tail
            newNode.previous = tail;
            //newNode will become new tail
            tail = newNode;
            //As it is last node, tail's next will point to null
            tail.next = null;
        }
    }
    
    //deleteFromStart() will delete a node from the beginning of the list
    public void deleteFromStart() {
        //Checks whether list is empty
        if(head == null) {
            return;
        }
        else {
            //Checks whether the list contains only one element
            if(head != tail) {
                //head will point to next node in the list
                head = head.next;
                //Previous node to current head will be made null
                head.previous = null;
            }
            //If the list contains only one element 
            //then, it will remove node and now both head and tail will point to null
            else {
                head = tail = null;
            }
        }
    }
    
    //display() will print out the nodes of the list
    public void display() {
        //Node current will point to head
        Node current = head;
        if(head == null) {
            System.out.println("List is empty");
            return;
        }
        while(current != null) {
            //Prints each node by incrementing the pointer.

            System.out.print(current.data + " ");
            current = current.next;
        }
        System.out.println();
    }
    
    public static void main(String[] args) {
        
        DeleteStart dList = new DeleteStart();
        //Add nodes to the list
        dList.addNode(1);
        dList.addNode(2);
        dList.addNode(3);
        dList.addNode(4);
        dList.addNode(5);
        
        //Printing original list
        System.out.println("Original List: ");
        dList.display();
        while(dList.head != null) {
            dList.deleteFromStart();
            //Printing updated list
            System.out.println("Updated List: ");
            dList.display();
        }
    }
}

输出

Original List: 
1 2 3 4 5 
Updated List: 
2 3 4 5 
Updated List: 
3 4 5 
Updated List: 
4 5 
Updated List: 
5 
Updated List: 
List is empty

C#

 using System; 
namespace DoublyLinkedList 
{                     
    public class Program
    {
        //Represent a node of the doubly linked list

        public class Node<T>{
            public T data;
            public Node<T> previous;
            public Node<T> next;
            
            public Node(T value) {
                data = value;
            }
        }
        
        public class DeleteStart<T>{
            //Represent the head and tail of the doubly linked list
            public Node<T> head = null;             
             public Node<T> tail = null;
            
            //addNode() will add a node to the list
            public void addNode(T data) {
                //Create a new node
                Node<T> newNode = new Node<T>(data);
 
                //If list is empty
                if(head == null) {
                    //Both head and tail will point to newNode
                    head = tail = newNode;
                    //head's previous will point to null
                    head.previous = null;
                    //tail's next will point to null, as it is the last node of the list
                    tail.next = null;
                }
                else {
                    //newNode will be added after tail such that tail's next will point to newNode
                    tail.next = newNode;
                    //newNode's previous will point to tail
                    newNode.previous = tail;
                    //newNode will become new tail
                    tail = newNode;
                    //As it is last node, tail's next will point to null
                    tail.next = null;
                }
            }
    
            //deleteFromStart() will delete a node from the beginning of the list
            public void deleteFromStart() {
                //Checks whether list is empty
                if(head == null) {
                    return;
                }
                else {
                    //Checks whether the list contains only one element
                    if(head != tail) {
                        //head will point to next node in the list
                        head = head.next;
                        //Previous node to current head will be made null
                        head.previous = null;
                    }
                    //If the list contains only one element 
                    //then, it will remove node and now both head and tail will point to null
                    else {
                        head = tail = null;
                    }
                }
            }
    
            //display() will print out the nodes of the list
            public void display() {
                //Node current will point to head
                Node<T> current = head;
                if(head == null) {
                    Console.WriteLine("List is empty");
                    return;
                }
                while(current != null) {
                    //Prints each node by incrementing the pointer.

                    Console.Write(current.data + " ");
                    current = current.next;
                }
                Console.WriteLine();
            }
        }
        
        public static void Main()
        {
            DeleteStart<int> dList = new DeleteStart<int>();
            //Add nodes to the list
            dList.addNode(1);
            dList.addNode(2);
            dList.addNode(3);
            dList.addNode(4);
            dList.addNode(5);
 
            //Printing original list
            Console.WriteLine("Original List: ");
            dList.display();
            while(dList.head != null) {
                dList.deleteFromStart();
                //Printing updated list
                Console.WriteLine("Updated List: ");
                dList.display();
            }
        }    
    }
}

输出

Original List: 
1 2 3 4 5 
Updated List: 
2 3 4 5 
Updated List: 
3 4 5 
Updated List: 
4 5 
Updated List: 
5 
Updated List: 
List is empty

PHP

<!DOCTYPE html>
<html>
<body>
<?php
//Represent a node of doubly linked list
class Node{
    public $data;
    public $previous;
    public $next;
    
    function __construct($data){
        $this->data = $data;
    }
}
class DeleteStart{
    //Represent the head and tail of the doubly linked list
    public $head;
    public $tail;
    function __construct(){
        $this->head = NULL;
        $this->tail = NULL;
    }
    
    //addNode() will add a node to the list
    function addNode($data) {
        //Create a new node
        $newNode = new Node($data);
        
        //If list is empty
        if($this->head == NULL) {
            //Both head and tail will point to newNode
            $this->head = $this->tail = $newNode;
            //head's previous will point to NULL
            $this->head->previous = NULL;
            //tail's next will point to NULL, as it is the last node of the list
            $this->tail->next = NULL;
        }
        else {
            //newNode will be added after tail such that tail's next will point to newNode
            $this->tail->next = $newNode;
            //newNode's previous will point to tail
            $newNode->previous = $this->tail;
            //newNode will become new tail
            $this->tail = $newNode;
            //As it is last node, tail's next will point to NULL
            $this->tail->next = NULL;
        }
    }
    
    //deleteFromStart() will delete a node from the beginning of the list
    function deleteFromStart() {
        //Checks whether list is empty
        if($this->head == NULL) {
            return;
        }
        else {
            //Checks whether the list contains only one element
            if($this->head != $this->tail) {
                //head will point to next node in the list
                $this->head = $this->head->next;
                //Previous node to current head will be made NULL
                $this->head->previous = NULL;
            }
            //If the list contains only one element 
            //then, it will remove node and now both head and tail will point to NULL
            else {
                $this->head = $this->tail = NULL;
            }
        }
    }
    
    //display() will print out the nodes of the list
    function display() {
        //Node current will point to head
        $current = $this->head;
        if($this->head == NULL) {
            print("List is empty <br>");
            return;
        }
        while($current != NULL) {
            //Prints each node by incrementing pointer.
            print($current->data . " ");
            $current = $current->next;
        }
        print("<br>");
    }
}
    
$dList = new DeleteStart();
//Add nodes to the list
$dList->addNode(1);
$dList->addNode(2);
$dList->addNode(3);
$dList->addNode(4);
$dList->addNode(5);
 
//Printing original list
print("Original List: <br>");
$dList->display();
while($dList->head != NULL) {
    $dList->deleteFromStart();
    //Printing updated list
    print("Updated List: <br>");
    $dList->display();
}
?>
</body>
</html>

输出

Original List: 
1 2 3 4 5 
Updated List: 
2 3 4 5 
Updated List: 
3 4 5 
Updated List: 
4 5 
Updated List: 
5 
Updated List: 
List is empty

下一主题#

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