C语言实现单链表-增删改查

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

// 链表节点结构体
typedef struct ListNode {
    int data;                   // 节点数据
    struct ListNode *next;      // 下一个节点的指针
} ListNode;

// 创建一个新节点
ListNode *createNode(int data) {
    ListNode *node = (ListNode*) malloc(sizeof(ListNode));
    node->data = data;
    node->next = NULL;
    return node;
}

// 在链表头部插入一个新节点
ListNode *insertNodeAtHead(ListNode *head, int data) {
    ListNode *node = createNode(data);
    node->next = head;
    return node;
}

// 在链表尾部插入一个新节点
ListNode *insertNodeAtTail(ListNode *head, int data) {
    ListNode *node = createNode(data);
    if(head == NULL) {
        return node;
    } else {
        ListNode *current = head;
        while(current->next != NULL) {
            current = current->next;
        }
        current->next = node;
        return head;
    }
}

// 删除链表中第一个值为data的节点
ListNode *deleteNode(ListNode *head, int data) {
    if(head == NULL) {
        return NULL;
    }
    if(head->data == data) {
        ListNode *current = head;
        head = head->next;
        free(current);
        return head;
    }
    ListNode *current = head;
    while(current->next != NULL && current->next->data != data) {
        current = current->next;
    }
    if(current->next != NULL) {
        ListNode *deleteNode = current->next;
        current->next = deleteNode->next;
        free(deleteNode);
    }
    return head;
}

// 修改链表中第一个值为oldData的节点的数据为newData
void updateNode(ListNode *head, int oldData, int newData) {
    ListNode *current = head;
    while(current != NULL) {
        if(current->data == oldData) {
            current->data = newData;
            break;
        } else {
            current = current->next;
        }
    }
}

// 遍历链表
void traverseList(ListNode *head) {
    ListNode *current = head;
    while(current != NULL) {
        printf("%d ", current->data);
        current = current->next;
    }
    printf("\n");
}

// 清空链表，释放所有节点的内存空间
void clearList(ListNode *head) {
    while(head != NULL) {
        ListNode *current = head;
        head = head->next;
        free(current);
    }
}

// 示例程序
int main() {
    ListNode *head = NULL;
    head = insertNodeAtHead(head, 1);
    head = insertNodeAtHead(head, 2);
    head = insertNodeAtTail(head, 3);
    traverseList(head);
    head = deleteNode(head, 2);
    traverseList(head);
    updateNode(head, 1, 4);
    traverseList(head);
    clearList(head);
    return 0;
}