数据结构示例-双向链表的开头插入新节点

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📜 数据结构示例-双向链表的开头插入新节点

📅 最后修改于: 2020-10-15 05:30:44 🧑 作者: Mango

问：程序在双链表的开头插入一个新节点。

说明

在此程序中，我们将创建一个双向链接列表，并将每个新节点插入列表的开头。如果列表为空，则头和尾将指向新添加的节点。如果列表不为空，则在列表的开头插入新节点，以便头的前一个节点指向新节点。将新节点作为列表的头，其前一个将指向null。

考虑上面的例子。最初，1是列表的头。现在，将在节点1之前插入new，以便节点1的前一个指向new。将new作为列表的开头，其上一个将指向null。

算法

定义一个Node类，该类代表列表中的一个节点。它具有三个属性：数据，前一个将指向上一个节点，下一个将指向下一个节点。
定义另一个用于创建双向链接列表的类，它具有两个节点：head和tail。最初，头和尾将指向null。
addAtStart()将节点添加到列表的开头：
1. 它首先检查head是否为空，然后将节点插入为head。
2. 头部和尾部都将指向新添加的节点。
3. 头的前一个指针将指向空，而头的下一个指针将指向空。
4. 如果head不为null，则head的前一个将指向新节点。
5. 将新节点作为列表的头部。
6. 由于新节点变为head，因此其先前节点应指向null。
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指向null。
3. 当前将在每次迭代中指向列表中的下一个节点。

示例：

Python

#Represent a node of doubly linked list
class Node:
    def __init__(self,data):
        self.data = data;
        self.previous = None;
        self.next = None;
        
class InsertStart:
    #Represent the head and tail of the doubly linked list
    def __init__(self):
        self.head = None;
        self.tail = None;
        
    #addAtStart() will add a node to the starting of the list
    def addAtStart(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;
        #Add newNode as new head of the list
        else:
            #head's previous node will be newNode
            self.head.previous = newNode;
            #newNode's next node will be head
            newNode.next = self.head;
            #newNode's previous will point to None
            newNode.previous = None;
            #newNode will become new head
            self.head = newNode;
            
    #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;
        print("Adding a node to the start of the list: ");
        while(current != None):
            #Prints each node by incrementing pointer.
            print(current.data),
            current = current.next;
            
        print();
        
dList = InsertStart();
 
#Adding 1 to the list
dList.addAtStart(1);
dList.display();
#Adding 2 to the list
dList.addAtStart(2);
dList.display();
#Adding 3 to the list
dList.addAtStart(3);
dList.display();
#Adding 4 to the list
dList.addAtStart(4);
dList.display();
#Adding 5 to the list
dList.addAtStart(5);
dList.display();

输出：

Adding a node to the start of the list: 
1 
Adding a node to the start of the list: 
2 1 
Adding a node to the start of the list: 
3 2 1 
Adding a node to the start of the list: 
4 3 2 1 
Adding a node to the start of the list: 
5 4 3 2 1

C

#include 
 
//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;
 
//addAtStart() will add a node to the starting of the list
void addAtStart(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;
    }
    //Add newNode as new head of the list
    else {
        //head's previous node will be newNode
        head->previous = newNode;
        //newNode's next node will be head
        newNode->next = head;
        //newNode's previous will point to NULL
        newNode->previous = NULL;
        //newNode will become new head
        head = newNode;
    }
}
 
//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;
    }
    printf("Adding a node to the start of the list: \n");
    while(current != NULL) {
        //Prints each node by incrementing pointer.
        printf("%d ", current->data);
        current = current->next;
    }
    printf("\n");
}
 
int main()
{
    //Adding 1 to the list
    addAtStart(1);
    display();
    //Adding 2 to the list
    addAtStart(2);
    display();
    //Adding 3 to the list
    addAtStart(3);
    display();
    //Adding 4 to the list
    addAtStart(4);
    display();
    //Adding 5 to the list
    addAtStart(5);
    display();
 
    return 0;
}

输出：

Adding a node to the start of the list: 
1 
Adding a node to the start of the list: 
2 1 
Adding a node to the start of the list: 
3 2 1 
Adding a node to the start of the list: 
4 3 2 1 
Adding a node to the start of the list: 
5 4 3 2 1

JAVA

public class InsertStart {
    
    //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;
    
    //addAtStart() will add a node to the starting of the list
    public void addAtStart(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;
        }
        //Add newNode as new head of the list
        else {
            //head's previous node will be newNode
            head.previous = newNode;
            //newNode's next node will be head
            newNode.next = head;
            //newNode's previous will point to null
            newNode.previous = null;
            //newNode will become new head
            head = newNode;
        }
    }
    
    //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;
        }
        System.out.println("Adding a node to the start of the list: ");
        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) {
        
        InsertStart dList = new InsertStart();
        
        //Adding 1 to the list
        dList.addAtStart(1);
        dList.display();
        //Adding 2 to the list
        dList.addAtStart(2);
        dList.display();
        //Adding 3 to the list
        dList.addAtStart(3);
        dList.display();
        //Adding 4 to the list
        dList.addAtStart(4);
        dList.display();
        //Adding 5 to the list
        dList.addAtStart(5);
        dList.display();
    }
}

输出：

Adding a node to the start of the list: 
1 
Adding a node to the start of the list: 
2 1 
Adding a node to the start of the list: 
3 2 1 
Adding a node to the start of the list: 
4 3 2 1 
Adding a node to the start of the list: 
5 4 3 2 1

C＃

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

        public class Node{
            public T data;
            public Node previous;
            public Node next;
            
            public Node(T value) {
                data = value;
            }
        }
        
        public class InsertStart{
            //Represent the head and tail of the doubly linked list
            protected Node head = null;             
             protected Node tail = null;
            
            //addAtStart() will add a node to the starting of the list
            public void addAtStart(T 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;
                }
                //Add newNode as new head of the list
                else {
                    //head's previous node will be newNode
                    head.previous = newNode;
                    //newNode's next node will be head
                    newNode.next = head;
                    //newNode's previous will point to null
                    newNode.previous = null;
                    //newNode will become new head
                    head = newNode;
                }
            }
    
            //display() will print out the nodes of the list
            public void display() {
                //Node current will point to head
                Node current = head;
                if(head == null) {
                    Console.WriteLine("List is empty");
                    return;
                }
                Console.WriteLine("Adding a node to the start of the list: ");
                while(current != null) {
                    //Prints each node by incrementing the pointer.

                    Console.Write(current.data + " ");
                    current = current.next;
                }
                Console.WriteLine();
            }
        }
        
        public static void Main()
        {
            InsertStart dList = new InsertStart();
 
            //Adding 1 to the list
            dList.addAtStart(1);
            dList.display();
            //Adding 2 to the list
            dList.addAtStart(2);
            dList.display();
            //Adding 3 to the list
            dList.addAtStart(3);
            dList.display();
            //Adding 4 to the list
            dList.addAtStart(4);
            dList.display();
            //Adding 5 to the list
            dList.addAtStart(5);
            dList.display();
        }    
    }
}

输出：

Adding a node to the start of the list: 
1 
Adding a node to the start of the list: 
2 1 
Adding a node to the start of the list: 
3 2 1 
Adding a node to the start of the list: 
4 3 2 1 
Adding a node to the start of the list: 
5 4 3 2 1

PHP：




data = $data;
    }
}
class InsertStart{
    //Represent the head and tail of the doubly linked list
    public $head;
    public $tail;
    function __construct(){
        $this->head = NULL;
        $this->tail = NULL;
    }
    
    //addAtStart() will add a node to the starting of the list
    function addAtStart($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;
        }
        //Add newNode as new head of the list
        else {
            //head's previous node will be newNode
            $this->head->previous = $newNode;
            //newNode's next node will be head
            $newNode->next = $this->head;
            //newNode's previous will point to NULL
            $newNode->previous = NULL;
            //newNode will become new head
            $this->head = $newNode;
        }
    }
    
    //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 
");
            return;
        }
        print("Adding a node to the start of the list: 
");
        while($current != NULL) {
            //Prints each node by incrementing pointer.
            print($current->data . " ");
            $current = $current->next;
        }
        print("
");
    }
}
    
$dList = new InsertStart();
 
//Adding 1 to the list
$dList->addAtStart(1);
$dList->display();
//Adding 2 to the list
$dList->addAtStart(2);
$dList->display();
//Adding 3 to the list
$dList->addAtStart(3);
$dList->display();
//Adding 4 to the list
$dList->addAtStart(4);
$dList->display();
//Adding 5 to the list
$dList->addAtStart(5);
$dList->display();
?>

输出：

Adding a node to the start of the list: 
1 
Adding a node to the start of the list: 
2 1 
Adding a node to the start of the list: 
3 2 1 
Adding a node to the start of the list: 
4 3 2 1 
Adding a node to the start of the list: 
5 4 3 2 1