C中循环链表上所有操作的程序

在循环链接列表中，每个元素都有到其序列中下一个元素的链接，而最后一个元素有至第一个元素的链接。循环链表与单链表相似，不同之处在于最后一个节点指向第一个节点。下图说明了这一点：

循环链表的一些常见操作在以下实现：

在开始处插入：插入一个新节点作为第一个节点。 last的下一个指针将指向该节点，而这个新节点将指向先前的第一个节点。

C

// C program for the above operation
#include 
#include 
  
// Structure of a linked list node
struct node {
    int info;
    struct node* next;
};
  
// Pointer to last node in the list
struct node* last = NULL;
  
// Function to insert a node in the
// starting of the list
void insertAtFront()
{
    // Stores the number to be inserted
    int data;
  
    // Initialize a new node
    struct node* temp;
    temp = (struct node*)malloc(sizeof(struct node));
  
    // Input data
    printf("\nEnter data to be "
           "inserted: \n");
    scanf("%d", &data);
  
    // If the new node is the only
    // node in the list
    if (last == NULL) {
        temp->info = data;
        temp->next = temp;
        last = temp;
    }
  
    // Else last node contains the
    // reference of the new node and
    // new node contains the reference
    // of the previous first node
    else {
        temp->info = data;
        temp->next = last->next;
  
        // last node now has reference
        // of the new node temp
        last->next = temp;
    }
}
  
// Function to print the list
void viewList()
{
    // If list is empty
    if (last == NULL)
        printf("\nList is empty\n");
  
    // Else print the list
    else {
        struct node* temp;
        temp = last->next;
  
        // While first node is not
        // reached again, print,
        // since the list is circular
        do {
            printf("\nData = %d", temp->info);
            temp = temp->next;
        } while (temp != last->next);
    }
}
  
// Driver Code
int main()
{
    // Function Call
    insertAtFront();
    insertAtFront();
    insertAtFront();
  
    // Print list
    viewList();
  
    return 0;
}

输出：

最后插入：插入一个新节点作为最后一个节点。 last的下一个指针将指向该节点，而这个新节点将指向第一个节点。

C

// C program for the above operation
#include 
#include 
  
// Structure of a linked list node
struct node {
    int info;
    struct node* next;
};
  
// Pointer to last node in the list
struct node* last = NULL;
  
// Function to add a new node at the
// end of the list
void addatlast()
{
    // Stores number to be inserted
    int data;
  
    // Initialize a new node
    struct node* temp;
    temp = (struct node*)malloc(sizeof(struct node));
  
    // Input data
    printf("\nEnter data to be "
           "inserted : \n");
    scanf("%d", &data);
  
    // If the new node is the
    // only node in the list
    if (last == NULL) {
        temp->info = data;
        temp->next = temp;
        last = temp;
    }
  
    // Else the new node will be the
    // last node and will contain
    // the reference of head node
    else {
        temp->info = data;
        temp->next = last->next;
        last->next = temp;
        last = temp;
    }
}
  
// Function to print the list
void viewList()
{
    // If list is empty
    if (last == NULL)
        printf("\nList is empty\n");
  
    // Else print the list
    else {
        struct node* temp;
        temp = last->next;
        do {
            printf("\nData = %d",
                   temp->info);
            temp = temp->next;
        } while (temp != last->next);
    }
}
  
// Driver Code
int main()
{
    // Function Call
    addatlast();
    addatlast();
    addatlast();
  
    // Print list
    viewList();
  
    return 0;
}

输出：

在特定元素之后插入：以下是在链表中的指定节点之后插入节点的程序。

C

// C program for the above operation
#include 
#include 
  
// Structure of a linked list node
struct node {
    int info;
    struct node* next;
};
  
// Pointer to last node in list
struct node* last = NULL;
  
// Function to add a new node
// at the end of the list
void addatlast()
{
    // Stores number to be inserted
    int data;
  
    // Initialize a new node
    struct node* temp;
    temp = (struct node*)malloc(sizeof(struct node));
  
    // Input data
    printf("\nEnter data to be inserted : \n");
    scanf("%d", &data);
  
    // If the new node is the
    // only node in the list
    if (last == NULL) {
        temp->info = data;
        temp->next = temp;
        last = temp;
    }
  
    // Else the new node will be the
    // last node and will contain
    // the reference of head node
    else {
        temp->info = data;
        temp->next = last->next;
        last->next = temp;
        last = temp;
    }
}
  
// Function to insert after any
// specified element
void insertafter()
{
    // Stores data and element after
    // which new node is to be inserted
    int data, value;
  
    // Initialize a new node
    struct node *temp, *n;
  
    // Input data
    printf("\nEnter number after which"
           " you want to enter number: \n");
    scanf("%d", &value);
    temp = last->next;
  
    do {
  
        // Element after which node is
        // to be inserted is found
        if (temp->info == value) {
            n = (struct node*)malloc(sizeof(struct node));
  
            // Input Data
            printf("\nEnter data to be"
                   " inserted : \n");
            scanf("%d", &data);
            n->info = data;
            n->next = temp->next;
            temp->next = n;
  
            // If temp is the last node
            // so now n will become the
            // last node
            if (temp == last)
                last = n;
            break;
        }
        else
            temp = temp->next;
    } while (temp != last->next);
}
  
// Function to print the list
void viewList()
{
    // If list is empty
    if (last == NULL)
        printf("\nList is empty\n");
  
    // Else print the list
    else {
        struct node* temp;
        temp = last->next;
        do {
            printf("\nData = %d",
                   temp->info);
            temp = temp->next;
        } while (temp != last->next);
    }
}
  
// Driver Code
int main()
{
    // Initialize the list
    addatlast();
    addatlast();
    addatlast();
  
    // Function Call
    insertafter();
  
    // Print list
    viewList();
  
    return 0;
}

输出：

删除第一个元素：删除链表的第一个节点。为此，last的下一个指针将指向链接列表的第二个节点。以下是相同的程序：

C

// C program for the above operation
#include 
#include 
  
// Structure of a linked list node
struct node {
    int info;
    struct node* next;
};
  
// Pointer to last node in list
struct node* last = NULL;
  
// Function to add a new node
// at the end of the list
void addatlast()
{
    // Stores number to be inserted
    int data;
  
    // Initialize a new node
    struct node* temp;
    temp = (struct node*)malloc(sizeof(struct node));
  
    // Input data
    printf("\nEnter data to be"
           " inserted: \n");
    scanf("%d", &data);
  
    // If the new node is the only
    // node in the list
    if (last == NULL) {
        temp->info = data;
        temp->next = temp;
        last = temp;
    }
  
    // Else the new node will be the
    // last node and will contain
    // the reference of head node
    else {
        temp->info = data;
        temp->next = last->next;
        last->next = temp;
        last = temp;
    }
}
  
// Function to delete the first
// element of the list
void deletefirst()
{
    struct node* temp;
  
    // If list is empty
    if (last == NULL)
        printf("\nList is empty.\n");
  
    // Else last node now contains
    // reference of the second node
    // in the list because the
    // list is circular
    else {
        temp = last->next;
        last->next = temp->next;
        free(temp);
    }
}
  
// Function to print the list
void viewList()
{
    // If list is empty
    if (last == NULL)
        printf("\nList is empty\n");
  
    // Else print the list
    else {
        struct node* temp;
        temp = last->next;
        do {
            printf("\nData = %d",
                   temp->info);
            temp = temp->next;
        } while (temp != last->next);
    }
}
  
// Driver Code
int main()
{
    // Initialize the list
    addatlast();
    addatlast();
    addatlast();
  
    // Function Call
    deletefirst();
  
    // Print list
    viewList();
  
    return 0;
}

输出：

删除最后一个元素：删除链接列表的最后一个节点。为此，倒数第二个节点将指向列表的第一个节点。以下是相同的程序：

C

// C program for the above operation
#include 
#include 
  
// Structure of a linked list node
struct node {
    int info;
    struct node* next;
};
  
// Pointer to last node in list
struct node* last = NULL;
  
// Function to add a new node
// at the end of the list
void addatlast()
{
    // Stores number to be inserted
    int data;
  
    // Initialize a new node
    struct node* temp;
    temp = (struct node*)malloc(sizeof(struct node));
  
    // Input data
    printf("\nEnter data to be inserted : \n");
    scanf("%d", &data);
  
    // If the new node is the only
    // node in the list
    if (last == NULL) {
        temp->info = data;
        temp->next = temp;
        last = temp;
    }
  
    // Else the new node will be
    // last node and will contain
    // the reference of head node
    else {
        temp->info = data;
        temp->next = last->next;
        last->next = temp;
        last = temp;
    }
}
  
// Funtion to delete the last node
// in the list
void deletelast()
{
    struct node* temp;
  
    // If list is empty
    if (last == NULL)
        printf("\nList is empty.\n");
  
    temp = last->next;
  
    // Traverse the list till
    // the second last node
    while (temp->next != last)
        temp = temp->next;
  
    // Second last node now contains
    // the reference of the first
    // node in the list
    temp->next = last->next;
    last = temp;
}
  
// Function to print the list
void viewList()
{
    // If list is empty
    if (last == NULL)
        printf("\nList is empty\n");
  
    // Else print the list
    else {
        struct node* temp;
        temp = last->next;
        do {
            printf("\nData = %d",
                   temp->info);
            temp = temp->next;
        } while (temp != last->next);
    }
}
  
// Driver Code
int main()
{
    // Initialize the list
    addatlast();
    addatlast();
    addatlast();
  
    // Function Call
    deletelast();
  
    // Print the list
    viewList();
  
    return 0;
}

输出：

在给定位置删除：从链接列表中的指定位置删除元素。以下是相同的程序：

C

// C program for the above operation
#include 
#include 
  
// Structure of a linked list node
struct node {
    int info;
    struct node* next;
};
  
// Pointer to last node in list
struct node* last = NULL;
  
// Function to add a new node
// at the end of the list
void addatlast()
{
    // Stores number to be inserted
    int data;
  
    // Initialize a new node
    struct node* temp;
    temp = (struct node*)malloc(sizeof(struct node));
  
    // Input data
    printf("\nEnter data to be inserted : \n");
    scanf("%d", &data);
  
    // If the new node is the
    // only node in the list
    if (last == NULL) {
        temp->info = data;
        temp->next = temp;
        last = temp;
    }
  
    // Else the new node will be
    // last node and will contain
    // the reference of head node
    else {
        temp->info = data;
        temp->next = last->next;
        last->next = temp;
        last = temp;
    }
}
  
// Function to delete an element
// at a specified index in the list
void deleteAtIndex()
{
    // Stores the index at which
    // the element is to be deleted
    int pos, i = 1;
    struct node *temp, *position;
    temp = last->next;
  
    // If list is empty
    if (last == NULL)
        printf("\nList is empty.\n");
  
    // Else
    else {
  
        // Input Data
        printf("\nEnter index : ");
        scanf("%d", &pos);
  
        // Traverse till the node to
        // be deleted is reached
        while (i <= pos - 1) {
            temp = temp->next;
            i++;
        }
  
        // After the loop ends, temp
        // points at a node just before
        // the node to be deleted
  
        // Reassigning links
        position = temp->next;
        temp->next = position->next;
  
        free(position);
    }
}
  
// Function to print the list
void viewList()
{
    // If list is empty
    if (last == NULL)
        printf("\nList is empty\n");
  
    // Else print the list
    else {
        struct node* temp;
        temp = last->next;
        do {
            printf("\nData = %d", temp->info);
            temp = temp->next;
        } while (temp != last->next);
    }
}
  
// Driver Code
int main()
{
    // Initialize the list
    addatlast();
    addatlast();
    addatlast();
  
    // Function Call
    deleteAtIndex();
  
    // Print the list
    viewList();
  
    return 0;
}

输出：

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