C语言双向链表是什么及怎么实现

发布时间：2022-05-26 14:10:57 作者：iii
来源：亿速云阅读：189

C语言双向链表是什么及怎么实现

什么是双向链表

双向链表（Doubly Linked List）是一种常见的数据结构，它由一系列节点组成，每个节点包含两个指针：一个指向前一个节点（prev），另一个指向下一个节点（next）。与单向链表不同，双向链表可以从任意一个节点向前或向后遍历整个链表。

双向链表的主要特点包括： - 双向遍历：可以从头到尾或从尾到头遍历链表。 - 插入和删除操作高效：由于每个节点都保存了前驱和后继节点的信息，插入和删除操作的时间复杂度为 O(1)。 - 占用更多内存：每个节点需要额外的指针来存储前驱节点的地址，因此比单向链表占用更多的内存。

双向链表的结构

在C语言中，双向链表的节点通常定义为一个结构体，包含数据域和两个指针域：

struct Node {
    int data;           // 数据域
    struct Node* prev;  // 指向前一个节点的指针
    struct Node* next;  // 指向下一个节点的指针
};

双向链表的实现

1. 创建节点

首先，我们需要一个函数来创建新的节点：

#include <stdio.h>
#include <stdlib.h>

struct Node {
    int data;
    struct Node* prev;
    struct Node* next;
};

struct Node* createNode(int data) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    if (newNode == NULL) {
        printf("Memory allocation failed\n");
        exit(1);
    }
    newNode->data = data;
    newNode->prev = NULL;
    newNode->next = NULL;
    return newNode;
}

2. 插入节点

在链表头部插入节点

void insertAtHead(struct Node** head, int data) {
    struct Node* newNode = createNode(data);
    if (*head == NULL) {
        *head = newNode;
    } else {
        newNode->next = *head;
        (*head)->prev = newNode;
        *head = newNode;
    }
}

在链表尾部插入节点

void insertAtTail(struct Node** head, int data) {
    struct Node* newNode = createNode(data);
    if (*head == NULL) {
        *head = newNode;
    } else {
        struct Node* temp = *head;
        while (temp->next != NULL) {
            temp = temp->next;
        }
        temp->next = newNode;
        newNode->prev = temp;
    }
}

在指定位置插入节点

void insertAtPosition(struct Node** head, int data, int position) {
    if (position < 1) {
        printf("Invalid position\n");
        return;
    }
    if (position == 1) {
        insertAtHead(head, data);
        return;
    }
    struct Node* newNode = createNode(data);
    struct Node* temp = *head;
    for (int i = 1; i < position - 1 && temp != NULL; i++) {
        temp = temp->next;
    }
    if (temp == NULL) {
        printf("Position out of range\n");
        return;
    }
    newNode->next = temp->next;
    if (temp->next != NULL) {
        temp->next->prev = newNode;
    }
    temp->next = newNode;
    newNode->prev = temp;
}

3. 删除节点

删除头节点

void deleteAtHead(struct Node** head) {
    if (*head == NULL) {
        printf("List is empty\n");
        return;
    }
    struct Node* temp = *head;
    *head = (*head)->next;
    if (*head != NULL) {
        (*head)->prev = NULL;
    }
    free(temp);
}

删除尾节点

void deleteAtTail(struct Node** head) {
    if (*head == NULL) {
        printf("List is empty\n");
        return;
    }
    struct Node* temp = *head;
    while (temp->next != NULL) {
        temp = temp->next;
    }
    if (temp->prev != NULL) {
        temp->prev->next = NULL;
    } else {
        *head = NULL;
    }
    free(temp);
}

删除指定位置的节点

void deleteAtPosition(struct Node** head, int position) {
    if (*head == NULL || position < 1) {
        printf("List is empty or invalid position\n");
        return;
    }
    struct Node* temp = *head;
    if (position == 1) {
        deleteAtHead(head);
        return;
    }
    for (int i = 1; i < position && temp != NULL; i++) {
        temp = temp->next;
    }
    if (temp == NULL) {
        printf("Position out of range\n");
        return;
    }
    if (temp->next != NULL) {
        temp->next->prev = temp->prev;
    }
    if (temp->prev != NULL) {
        temp->prev->next = temp->next;
    }
    free(temp);
}

4. 遍历链表

从头到尾遍历

void printListForward(struct Node* head) {
    struct Node* temp = head;
    while (temp != NULL) {
        printf("%d -> ", temp->data);
        temp = temp->next;
    }
    printf("NULL\n");
}

从尾到头遍历

void printListBackward(struct Node* head) {
    struct Node* temp = head;
    if (temp == NULL) {
        printf("List is empty\n");
        return;
    }
    while (temp->next != NULL) {
        temp = temp->next;
    }
    while (temp != NULL) {
        printf("%d -> ", temp->data);
        temp = temp->prev;
    }
    printf("NULL\n");
}

5. 释放链表

为了避免内存泄漏，我们需要在程序结束时释放链表占用的内存：

void freeList(struct Node** head) {
    struct Node* temp;
    while (*head != NULL) {
        temp = *head;
        *head = (*head)->next;
        free(temp);
    }
}

完整示例

#include <stdio.h>
#include <stdlib.h>

struct Node {
    int data;
    struct Node* prev;
    struct Node* next;
};

struct Node* createNode(int data) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    if (newNode == NULL) {
        printf("Memory allocation failed\n");
        exit(1);
    }
    newNode->data = data;
    newNode->prev = NULL;
    newNode->next = NULL;
    return newNode;
}

void insertAtHead(struct Node** head, int data) {
    struct Node* newNode = createNode(data);
    if (*head == NULL) {
        *head = newNode;
    } else {
        newNode->next = *head;
        (*head)->prev = newNode;
        *head = newNode;
    }
}

void insertAtTail(struct Node** head, int data) {
    struct Node* newNode = createNode(data);
    if (*head == NULL) {
        *head = newNode;
    } else {
        struct Node* temp = *head;
        while (temp->next != NULL) {
            temp = temp->next;
        }
        temp->next = newNode;
        newNode->prev = temp;
    }
}

void insertAtPosition(struct Node** head, int data, int position) {
    if (position < 1) {
        printf("Invalid position\n");
        return;
    }
    if (position == 1) {
        insertAtHead(head, data);
        return;
    }
    struct Node* newNode = createNode(data);
    struct Node* temp = *head;
    for (int i = 1; i < position - 1 && temp != NULL; i++) {
        temp = temp->next;
    }
    if (temp == NULL) {
        printf("Position out of range\n");
        return;
    }
    newNode->next = temp->next;
    if (temp->next != NULL) {
        temp->next->prev = newNode;
    }
    temp->next = newNode;
    newNode->prev = temp;
}

void deleteAtHead(struct Node** head) {
    if (*head == NULL) {
        printf("List is empty\n");
        return;
    }
    struct Node* temp = *head;
    *head = (*head)->next;
    if (*head != NULL) {
        (*head)->prev = NULL;
    }
    free(temp);
}

void deleteAtTail(struct Node** head) {
    if (*head == NULL) {
        printf("List is empty\n");
        return;
    }
    struct Node* temp = *head;
    while (temp->next != NULL) {
        temp = temp->next;
    }
    if (temp->prev != NULL) {
        temp->prev->next = NULL;
    } else {
        *head = NULL;
    }
    free(temp);
}

void deleteAtPosition(struct Node** head, int position) {
    if (*head == NULL || position < 1) {
        printf("List is empty or invalid position\n");
        return;
    }
    struct Node* temp = *head;
    if (position == 1) {
        deleteAtHead(head);
        return;
    }
    for (int i = 1; i < position && temp != NULL; i++) {
        temp = temp->next;
    }
    if (temp == NULL) {
        printf("Position out of range\n");
        return;
    }
    if (temp->next != NULL) {
        temp->next->prev = temp->prev;
    }
    if (temp->prev != NULL) {
        temp->prev->next = temp->next;
    }
    free(temp);
}

void printListForward(struct Node* head) {
    struct Node* temp = head;
    while (temp != NULL) {
        printf("%d -> ", temp->data);
        temp = temp->next;
    }
    printf("NULL\n");
}

void printListBackward(struct Node* head) {
    struct Node* temp = head;
    if (temp == NULL) {
        printf("List is empty\n");
        return;
    }
    while (temp->next != NULL) {
        temp = temp->next;
    }
    while (temp != NULL) {
        printf("%d -> ", temp->data);
        temp = temp->prev;
    }
    printf("NULL\n");
}

void freeList(struct Node** head) {
    struct Node* temp;
    while (*head != NULL) {
        temp = *head;
        *head = (*head)->next;
        free(temp);
    }
}

int main() {
    struct Node* head = NULL;

    insertAtHead(&head, 10);
    insertAtHead(&head, 20);
    insertAtTail(&head, 30);
    insertAtPosition(&head, 40, 2);

    printf("Forward traversal: ");
    printListForward(head);

    printf("Backward traversal: ");
    printListBackward(head);

    deleteAtHead(&head);
    deleteAtTail(&head);
    deleteAtPosition(&head, 2);

    printf("Forward traversal after deletion: ");
    printListForward(head);

    freeList(&head);

    return 0;
}

总结

双向链表是一种功能强大的数据结构，它允许我们在链表中进行双向遍历，并且在插入和删除操作时具有较高的效率。通过本文的介绍和示例代码，你应该已经掌握了如何在C语言中实现双向链表的基本操作。希望这篇文章对你理解和使用双向链表有所帮助！

C语言双向链表是什么及怎么实现

C语言双向链表是什么及怎么实现

什么是双向链表

双向链表的结构

双向链表的实现

1. 创建节点

2. 插入节点

在链表头部插入节点

在链表尾部插入节点

在指定位置插入节点

3. 删除节点

删除头节点

删除尾节点

删除指定位置的节点

4. 遍历链表

从头到尾遍历

从尾到头遍历

5. 释放链表

完整示例

总结

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