问：在双向链表中搜索元素程序

2025年3月17日 | 阅读 8 分钟

说明

在此程序中，我们需要在双向链表中搜索给定节点。

Program to search an element in a doubly linked list

要解决此问题，我们将使用一个名为 current 的节点遍历列表。Current 指向 head，并开始将要搜索的节点数据与当前节点数据进行比较。如果它们相等，则将标志设置为 true，并打印消息以及要搜索的节点的位置。

例如，在上表中，搜索节点 4 可以在位置 3 找到。

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。
addNode() 将向列表中添加节点。
1. 它首先检查头节点是否为 null，然后将节点作为头节点插入。
2. 头节点和尾节点都将指向新添加的节点。
3. 头节点的前一个指针将指向 null，尾节点的下一个指针将指向 null。
4. 如果头节点不为 null，则新节点将插入到列表的末尾，使得新节点的前一个指针将指向尾节点。
5. 新节点将成为新的尾节点。尾节点的下一个指针将指向 null。
searchNode() 将在列表中搜索节点
1. 变量 i 将跟踪要搜索节点的**位置**。
2. 变量 flag 将存储布尔值 false。
3. Current 将指向 head 节点。
4. 通过将 current 递增到 current.next 并将 i 递增到 i + 1 来迭代循环。
5. 将每个节点的数据与搜索的节点进行比较。如果找到匹配项，则将 flag 设置为 true。
6. 如果 flag 为 true，则打印搜索节点的索引。
7. 否则，打印消息“元素不在列表中”。

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 SearchList:
    #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;
            
    #searchNode() will search a given node in the list
    def searchNode(self, value):
        i = 1;
        flag = False;
        #Node current will point to head
        current = self.head;
        
        #Checks whether the list is empty
        if(self.head == None):
            print("List is empty");
            return;
            
        while(current != None):
            #Compare value to be searched with each node in the list
            if(current.data == value):
                flag = True;
                break;
            current = current.next;
            i = i + 1;
            
        if(flag):
            print("Node is present in the list at the position : " + str(i));
        else:
            print("Node is not present in the list");
        
dList = SearchList();
#Add nodes to the list
dList.addNode(1);
dList.addNode(5);
dList.addNode(4);
dList.addNode(2);
dList.addNode(3);
 
#Search for node 4 in the list
dList.searchNode(4);
 
#Search for node 9 in the list
dList.searchNode(9);

输出

Node is present in the list at the position : 3
Node is not present in the list

C

#include <stdio.h>
#include <stdbool.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;
    }
}
 
//searchNode() will search a given node in the list
void searchNode(int value) {
    int i = 1;
    bool flag = false;
    //Node current will point to head
    struct node *current = head;
    
    //Checks whether the list is empty
    if(head == NULL) {
        printf("List is empty\n");
        return;
    }
    while(current != NULL) {
        //Compare value to be searched with each node in the list
        if(current->data == value) {
            flag = true;
            break;
        }
        current = current->next;
        i++;
    }
    if(flag)
         printf("Node is present in the list at the position : %d\n", i);
    else
         printf("Node is not present in the list\n");
}
 
int main()
{
    //Add nodes to the list
    addNode(1);
    addNode(5);
    addNode(4);
    addNode(2);
    addNode(3);
    
    //Search for node 4 in the list
    searchNode(4);
    //Search for node 9 in the list
    searchNode(9);
 
    return 0;
}

输出

Node is present in the list at the position : 3
Node is not present in the list

JAVA

public class SearchList {
    
    //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;
        }
    }
    
    //searchNode() will search a given node in the list
    public void searchNode(int value) {
        int i = 1;
        boolean flag = false;
        //Node current will point to head
        Node current = head;
        
        //Checks whether the list is empty
        if(head == null) {
            System.out.println("List is empty");
            return;
        }
        while(current != null) {
            //Compare value to be searched with each node in the list
            if(current.data == value) {
                flag = true;
                break;
            }
            current = current.next;
            i++;
        }
        if(flag)
             System.out.println("Node is present in the list at the position : " + i);
        else
             System.out.println("Node is not present in the list");
    }
    
    public static void main(String[] args) {
        
        SearchList dList = new SearchList();
        //Add nodes to the list
        dList.addNode(1);
        dList.addNode(5);
        dList.addNode(4);
        dList.addNode(2);
        dList.addNode(3);
        
        //Search for node 4 in the list
        dList.searchNode(4);
        //Search for node 9 in the list
        dList.searchNode(9);
    }
}

输出

Node is present in the list at the position : 3
Node is not present in the list

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 SearchList<T>{
            //Represent the head and tail of the doubly linked list
            protected Node<T> head = null;             
             protected 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;
                }
            }
            
            //searchNode() will search a given node in the list
            public void searchNode(int value) {
                int i = 1;
                bool flag = false;
                //Node current will point to head
                Node<T> current = head;
 
                //Checks whether the list is empty
                if(head == null) {
                    Console.WriteLine("List is empty");
                    return;
                }
                while(current != null) {
                    //Compare value to be searched with each node in the list
                    if(current.data.Equals(value)) {
                        flag = true;
                        break;
                    }
                    current = current.next;
                    i++;
                }
                if(flag)
                    Console.WriteLine("Node is present in the list at the position : " + i);
                else
                    Console.WriteLine("Node is not present in the list");
            }
        }
        
        public static void Main()
        {
            SearchList<int> dList = new SearchList<int>();
            //Add nodes to the list
            dList.addNode(1);
            dList.addNode(5);
            dList.addNode(4);
            dList.addNode(2);
            dList.addNode(3);
 
            //Search for node 4 in the list
            dList.searchNode(4);
            //Search for node 9 in the list
            dList.searchNode(9);
        }    
    }
}

输出

Node is present in the list at the position : 3
Node is not present in the list

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 SearchList{
    //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;
        }
    }
    
    //searchNode() will search a given node in the list
    function searchNode($value) {
        $i = 1;
        $flag = false;
        //Node current will point to head
        $current = $this->head;
        
        //Checks whether the list is empty
        if($this->head == NULL) {
            print("List is empty");
            return;
        }
        while($current != NULL) {
            //Compare value to be searched with each node in the list
            if($current->data == $value) {
                $flag = true;
                break;
            }
            $current = $current->next;
            $i++;
        }
        if($flag)
             print("Node is present in the list at the position : " . $i);
        else
             print("Node is not present in the list");
    }
}
    
$dList = new SearchList();
//Add nodes to the list
$dList->addNode(1);
$dList->addNode(5);
$dList->addNode(4);
$dList->addNode(2);
$dList->addNode(3);
 
//Search for node 4 in the list
$dList->searchNode(4);
print("<br>");
//Search for node 9 in the list
$dList->searchNode(9);
?>
</body>
</html>

输出

Node is present in the list at the position : 3
Node is not present in the list

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问：在双向链表中搜索元素程序

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