链表 |第一套（介绍）

与数组一样，链表是一种线性数据结构。与数组不同，链表元素不存储在连续的位置；元素使用指针链接。

为什么是链表？
数组可用于存储类似类型的线性数据，但数组有以下限制。
1）数组的大小是固定的：所以我们必须提前知道元素数量的上限。此外，一般而言，分配的内存与使用情况无关，等于上限。
2)在元素数组中插入一个新元素是昂贵的，因为必须为新元素创建房间，并且必须移动现有元素才能创建房间。
例如，在一个系统中，如果我们在数组 id[] 中维护一个排序的 ID 列表。
id[] = [1000, 1010, 1050, 2000, 2040]。
而如果我们要插入一个新的ID 1005，那么为了保持排序顺序，我们必须将1000之后的所有元素（不包括1000）移动。
除非使用某些特殊技术，否则删除数组的代价也很高。例如，要删除 id[] 中的 1010，必须移动 1010 之后的所有内容。
相对于阵列的优势
1)动态尺寸
2)易于插入/删除
缺点：
1)不允许随机访问。我们必须从第一个节点开始按顺序访问元素。所以我们不能用它的默认实现有效地对链表进行二分搜索。在这里阅读。
2)列表的每个元素都需要额外的指针存储空间。
3) 对缓存不友好。由于数组元素是连续的位置，因此存在引用的局部性，而在链表的情况下则不存在。
表示：
链表由指向链表第一个节点的指针表示。第一个节点称为头部。如果链表为空，则头部的值为NULL。
列表中的每个节点至少由两部分组成：
1）数据
2）指向下一个节点的指针（或引用）
在 C 中，我们可以使用结构来表示节点。下面是一个带有整数数据的链表节点的例子。
在Java或 C# 中，LinkedList 可以表示为一个类，而一个 Node 可以表示为一个单独的类。 LinkedList 类包含一个 Node 类类型的引用。

C

// A linked list node
struct Node {
    int data;
    struct Node* next;
};

C++

class Node {
public:
    int data;
    Node* next;
};

Java

class LinkedList {
    Node head; // head of the list
 
    /* Linked list Node*/
    class Node {
        int data;
        Node next;
 
        // Constructor to create a new node
        // Next is by default initialized
        // as null
        Node(int d) { data = d; }
    }
}

Python

# Node class
class Node:
  
    # Function to initialize the node object
    def __init__(self, data):
        self.data = data  # Assign data
        self.next = None  # Initialize
                          # next as null
  
# Linked List class
class LinkedList:
    
    # Function to initialize the Linked
    # List object
    def __init__(self):
        self.head = None

C#

class LinkedList {
    // The first node(head) of the linked list
    // Will be an object of type Node (null by default)
    Node head;
 
    class Node {
        int data;
        Node next;
 
        // Constructor to create a new node
        Node(int d) { data = d; }
    }
}

C 中的第一个简单链表让我们创建一个具有 3 个节点的简单链表。

C++

// A simple CPP program to introduce
// a linked list
#include 
using namespace std;
 
class Node {
public:
    int data;
    Node* next;
};
 
// Program to create a simple linked
// list with 3 nodes
int main()
{
    Node* head = NULL;
    Node* second = NULL;
    Node* third = NULL;
 
    // allocate 3 nodes in the heap
    head = new Node();
    second = new Node();
    third = new Node();
 
    /* Three blocks have been allocated dynamically.
    We have pointers to these three blocks as head,
    second and third    
    head         second         third
        |             |             |
        |             |             |
    +---+-----+     +----+----+     +----+----+
    | # | # |     | # | # |     | # | # |
    +---+-----+     +----+----+     +----+----+
     
# represents any random value.
Data is random because we haven’t assigned
anything yet */
 
    head->data = 1; // assign data in first node
    head->next = second; // Link first node with
    // the second node
 
    /* data has been assigned to the data part of first
    block (block pointed by the head). And next
    pointer of the first block points to second.
    So they both are linked.
 
    head         second         third
        |             |             |
        |             |             |
    +---+---+     +----+----+     +-----+----+
    | 1 | o----->| # | # |     | # | # |
    +---+---+     +----+----+     +-----+----+    
*/
 
    // assign data to second node
    second->data = 2;
 
    // Link second node with the third node
    second->next = third;
 
    /* data has been assigned to the data part of the second
    block (block pointed by second). And next
    pointer of the second block points to the third
    block. So all three blocks are linked.
     
    head         second         third
        |             |             |
        |             |             |
    +---+---+     +---+---+     +----+----+
    | 1 | o----->| 2 | o-----> | # | # |
    +---+---+     +---+---+     +----+----+     */
 
    third->data = 3; // assign data to third node
    third->next = NULL;
 
    /* data has been assigned to the data part of the third
    block (block pointed by third). And next pointer
    of the third block is made NULL to indicate
    that the linked list is terminated here.
 
    We have the linked list ready.
 
        head    
            |
            |
        +---+---+     +---+---+     +----+------+
        | 1 | o----->| 2 | o-----> | 3 | NULL |
        +---+---+     +---+---+     +----+------+    
     
     
    Note that only the head is sufficient to represent
    the whole list. We can traverse the complete
    list by following the next pointers. */
 
    return 0;
}
 
// This code is contributed by rathbhupendra

C

// A simple C program to introduce
// a linked list
#include 
#include 
 
struct Node {
    int data;
    struct Node* next;
};
 
// Program to create a simple linked
// list with 3 nodes
int main()
{
    struct Node* head = NULL;
    struct Node* second = NULL;
    struct Node* third = NULL;
 
    // allocate 3 nodes in the heap
    head = (struct Node*)malloc(sizeof(struct Node));
    second = (struct Node*)malloc(sizeof(struct Node));
    third = (struct Node*)malloc(sizeof(struct Node));
 
    /* Three blocks have been allocated dynamically.
     We have pointers to these three blocks as head,
     second and third    
       head           second           third
        |                |               |
        |                |               |
    +---+-----+     +----+----+     +----+----+
    | #  | #  |     | #  | #  |     |  # |  # |
    +---+-----+     +----+----+     +----+----+
    
   # represents any random value.
   Data is random because we haven’t assigned
   anything yet  */
 
    head->data = 1; // assign data in first node
    head->next = second; // Link first node with
    // the second node
 
    /* data has been assigned to the data part of the first
     block (block pointed by the head). And next
     pointer of first block points to second. 
     So they both are linked.
 
       head          second         third
        |              |              |
        |              |              |
    +---+---+     +----+----+     +-----+----+
    | 1  | o----->| #  | #  |     |  #  | #  |
    +---+---+     +----+----+     +-----+----+   
  */
 
    // assign data to second node
    second->data = 2;
 
    // Link second node with the third node
    second->next = third;
 
    /* data has been assigned to the data part of the second
     block (block pointed by second). And next
     pointer of the second block points to the third
     block. So all three blocks are linked.
   
       head         second         third
        |             |             |
        |             |             |
    +---+---+     +---+---+     +----+----+
    | 1  | o----->| 2 | o-----> |  # |  # |
    +---+---+     +---+---+     +----+----+      */
 
    third->data = 3; // assign data to third node
    third->next = NULL;
 
    /* data has been assigned to data part of third
    block (block pointed by third). And next pointer
    of the third block is made NULL to indicate
    that the linked list is terminated here.
 
     We have the linked list ready. 
 
           head   
             |
             |
        +---+---+     +---+---+       +----+------+
        | 1  | o----->|  2  | o-----> |  3 | NULL |
        +---+---+     +---+---+       +----+------+      
    
     
    Note that only head is sufficient to represent
    the whole list.  We can traverse the complete
    list by following next pointers.    */
 
    return 0;
}

Java

// A simple Java program to introduce a linked list
class LinkedList {
    Node head; // head of list
 
    /* Linked list Node.  This inner class is made static so that
       main() can access it */
    static class Node {
        int data;
        Node next;
        Node(int d)
        {
            data = d;
            next = null;
        } // Constructor
    }
 
    /* method to create a simple linked list with 3 nodes*/
    public static void main(String[] args)
    {
        /* Start with the empty list. */
        LinkedList llist = new LinkedList();
 
        llist.head = new Node(1);
        Node second = new Node(2);
        Node third = new Node(3);
 
        /* Three nodes have been allocated dynamically.
          We have references to these three blocks as head, 
          second and third
 
          llist.head        second              third
             |                |                  |
             |                |                  |
         +----+------+     +----+------+     +----+------+
         | 1  | null |     | 2  | null |     |  3 | null |
         +----+------+     +----+------+     +----+------+ */
 
        llist.head.next = second; // Link first node with the second node
 
        /*  Now next of the first Node refers to the second.  So they
            both are linked.
 
         llist.head        second              third
            |                |                  |
            |                |                  |
        +----+------+     +----+------+     +----+------+
        | 1  |  o-------->| 2  | null |     |  3 | null |
        +----+------+     +----+------+     +----+------+ */
 
        second.next = third; // Link second node with the third node
 
        /*  Now next of the second Node refers to third.  So all three
            nodes are linked.
 
         llist.head        second              third
            |                |                  |
            |                |                  |
        +----+------+     +----+------+     +----+------+
        | 1  |  o-------->| 2  |  o-------->|  3 | null |
        +----+------+     +----+------+     +----+------+ */
    }
}

Python

# A simple Python program to introduce a linked list
 
# Node class
class Node:
 
    # Function to initialise the node object
    def __init__(self, data):
        self.data = data  # Assign data
        self.next = None  # Initialize next as null
 
 
# Linked List class contains a Node object
class LinkedList:
 
    # Function to initialize head
    def __init__(self):
        self.head = None
 
 
# Code execution starts here
if __name__=='__main__':
 
    # Start with the empty list
    llist = LinkedList()
 
    llist.head = Node(1)
    second = Node(2)
    third = Node(3)
 
    '''
    Three nodes have been created.
    We have references to these three blocks as head,
    second and third
 
    llist.head        second              third
         |                |                  |
         |                |                  |
    +----+------+     +----+------+     +----+------+
    | 1  | None |     | 2  | None |     |  3 | None |
    +----+------+     +----+------+     +----+------+
    '''
 
    llist.head.next = second; # Link first node with second
 
    '''
    Now next of first Node refers to second.  So they
    both are linked.
 
    llist.head        second              third
         |                |                  |
         |                |                  |
    +----+------+     +----+------+     +----+------+
    | 1  |  o-------->| 2  | null |     |  3 | null |
    +----+------+     +----+------+     +----+------+
    '''
 
    second.next = third; # Link second node with the third node
 
    '''
    Now next of second Node refers to third.  So all three
    nodes are linked.
 
    llist.head        second              third
         |                |                  |
         |                |                  |
    +----+------+     +----+------+     +----+------+
    | 1  |  o-------->| 2  |  o-------->|  3 | null |
    +----+------+     +----+------+     +----+------+
    '''

C＃

// A simple C# program to introduce a linked list
using System;
 
public class LinkedList {
    Node head; // head of list
 
    /* Linked list Node. This inner class is made static so that
    main() can access it */
    public class Node {
        public int data;
        public Node next;
        public Node(int d)
        {
            data = d;
            next = null;
        } // Constructor
    }
 
    /* method to create a simple linked list with 3 nodes*/
    public static void Main(String[] args)
    {
        /* Start with the empty list. */
        LinkedList llist = new LinkedList();
 
        llist.head = new Node(1);
        Node second = new Node(2);
        Node third = new Node(3);
 
        /* Three nodes have been allocated dynamically.
        We have references to these three blocks as head,
        second and third
 
        llist.head     second             third
            |             |                 |
            |             |                 |
        +----+------+     +----+------+     +----+------+
        | 1 | null |     | 2 | null |     | 3 | null |
        +----+------+     +----+------+     +----+------+ */
 
        llist.head.next = second; // Link first node with the second node
 
        /* Now next of first Node refers to second. So they
            both are linked.
 
        llist.head     second             third
            |             |                 |
            |             |                 |
        +----+------+     +----+------+     +----+------+
        | 1 | o-------->| 2 | null |     | 3 | null |
        +----+------+     +----+------+     +----+------+ */
 
        second.next = third; // Link second node with the third node
 
        /* Now next of the second Node refers to third. So all three
            nodes are linked.
 
        llist.head     second             third
            |             |                 |
            |             |                 |
        +----+------+     +----+------+     +----+------+
        | 1 | o-------->| 2 | o-------->| 3 | null |
        +----+------+     +----+------+     +----+------+ */
    }
}
 
// This code has been contributed by 29AjayKumar

链表遍历
在前面的程序中，我们创建了一个简单的带有三个节点的链表。让我们遍历创建的列表并打印每个节点的数据。对于遍历，让我们编写一个通用函数printList() 来打印任何给定的列表。

我们强烈建议您在继续解决方案之前单击此处进行练习。

C++

// A simple C++ program for traversal of a linked list
#include 
using namespace std;
 
class Node {
public:
    int data;
    Node* next;
};
 
// This function prints contents of linked list
// starting from the given node
void printList(Node* n)
{
    while (n != NULL) {
        cout << n->data << " ";
        n = n->next;
    }
}
 
// Driver code
int main()
{
    Node* head = NULL;
    Node* second = NULL;
    Node* third = NULL;
 
    // allocate 3 nodes in the heap
    head = new Node();
    second = new Node();
    third = new Node();
 
    head->data = 1; // assign data in first node
    head->next = second; // Link first node with second
 
    second->data = 2; // assign data to second node
    second->next = third;
 
    third->data = 3; // assign data to third node
    third->next = NULL;
 
    printList(head);
 
    return 0;
}
 
// This is code is contributed by rathbhupendra

C

// A simple C program for traversal of a linked list
#include 
#include 
 
struct Node {
    int data;
    struct Node* next;
};
 
// This function prints contents of linked list starting from
// the given node
void printList(struct Node* n)
{
    while (n != NULL) {
        printf(" %d ", n->data);
        n = n->next;
    }
}
 
int main()
{
    struct Node* head = NULL;
    struct Node* second = NULL;
    struct Node* third = NULL;
 
    // allocate 3 nodes in the heap
    head = (struct Node*)malloc(sizeof(struct Node));
    second = (struct Node*)malloc(sizeof(struct Node));
    third = (struct Node*)malloc(sizeof(struct Node));
 
    head->data = 1; // assign data in first node
    head->next = second; // Link first node with second
 
    second->data = 2; // assign data to second node
    second->next = third;
 
    third->data = 3; // assign data to third node
    third->next = NULL;
 
    printList(head);
 
    return 0;
}

Java

// A simple Java program for traversal of a linked list
class LinkedList {
    Node head; // head of list
 
    /* Linked list Node.  This inner class is made static so that
       main() can access it */
    static class Node {
        int data;
        Node next;
        Node(int d)
        {
            this.data = d;
            next = null;
        } // Constructor
    }
 
    /* This function prints contents of linked list starting from head */
    public void printList()
    {
        Node n = head;
        while (n != null) {
            System.out.print(n.data + " ");
            n = n.next;
        }
    }
 
    /* method to create a simple linked list with 3 nodes*/
    public static void main(String[] args)
    {
        /* Start with the empty list. */
        LinkedList llist = new LinkedList();
 
        llist.head = new Node(1);
        Node second = new Node(2);
        Node third = new Node(3);
 
        llist.head.next = second; // Link first node with the second node
        second.next = third; // Link second node with the third node
 
        llist.printList();
    }
}

蟒蛇3

# A simple Python program for traversal of a linked list
 
# Node class
class Node:
 
    # Function to initialise the node object
    def __init__(self, data):
        self.data = data  # Assign data
        self.next = None  # Initialize next as null
 
 
# Linked List class contains a Node object
class LinkedList:
 
    # Function to initialize head
    def __init__(self):
        self.head = None
 
    # This function prints contents of linked list
    # starting from head
    def printList(self):
        temp = self.head
        while (temp):
            print (temp.data)
            temp = temp.next
 
 
# Code execution starts here
if __name__=='__main__':
 
    # Start with the empty list
    llist = LinkedList()
 
    llist.head = Node(1)
    second = Node(2)
    third = Node(3)
 
    llist.head.next = second; # Link first node with second
    second.next = third; # Link second node with the third node
 
    llist.printList()

C＃

// A simple C# program for traversal of a linked list
using System;
 
public class LinkedList {
    Node head; // head of list
 
    /* Linked list Node. This inner
    class is made static so that
    main() can access it */
    public class Node {
        public int data;
        public Node next;
        public Node(int d)
        {
            data = d;
            next = null;
 
        } // Constructor
    }
 
    /* This function prints contents of
    linked list starting from head */
    public void printList()
    {
        Node n = head;
        while (n != null) {
            Console.Write(n.data + " ");
            n = n.next;
        }
    }
 
    /* method to create a simple linked list with 3 nodes*/
    public static void Main(String[] args)
    {
        /* Start with the empty list. */
        LinkedList llist = new LinkedList();
 
        llist.head = new Node(1);
        Node second = new Node(2);
        Node third = new Node(3);
 
        llist.head.next = second; // Link first node with the second node
        second.next = third; // Link second node with the third node
 
        llist.printList();
    }
}
 
/* This code contributed by PrinciRaj1992 */

输出：

1  2  3

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