实现带头结点的单链表的建立、求长度，取元素、修改元素、插入、删除等单链表的基本操作。c语言代码

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

typedef struct Node {
    int data;
    struct Node* next;
} Node, *LinkedList;

LinkedList createLinkedList() {
    LinkedList head = (LinkedList)malloc(sizeof(Node));
    head->next = NULL;
    return head;
}

int length(LinkedList head) {
    int len = 0;
    Node* p = head->next;
    while (p != NULL) {
        len++;
        p = p->next;
    }
    return len;
}

Node* getElement(LinkedList head, int index) {
    if (index < 0 || index >= length(head)) {
        printf("Invalid index\n");
        return NULL;
    }
    Node* p = head->next;
    int i = 0;
    while (p != NULL && i < index) {
        p = p->next;
        i++;
    }
    return p;
}

void modifyElement(LinkedList head, int index, int value) {
    Node* p = getElement(head, index);
    if (p != NULL) {
        p->data = value;
    }
}

void insertElement(LinkedList head, int index, int value) {
    if (index < 0 || index > length(head)) {
        printf("Invalid index\n");
        return;
    }
    Node* p = head;
    int i = 0;
    while (p != NULL && i < index) {
        p = p->next;
        i++;
    }
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->data = value;
    newNode->next = p->next;
    p->next = newNode;
}

void deleteElement(LinkedList head, int index) {
    if (index < 0 || index >= length(head)) {
        printf("Invalid index\n");
        return;
    }
    Node* p = head;
    int i = 0;
    while (p->next != NULL && i < index) {
        p = p->next;
        i++;
    }
    Node* q = p->next;
    p->next = q->next;
    free(q);
}

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

void destroyLinkedList(LinkedList head) {
    Node* p = head;
    while (p != NULL) {
        Node* q = p;
        p = p->next;
        free(q);
    }
}

int main() {
    LinkedList head = createLinkedList();
    insertElement(head, 0, 1);
    insertElement(head, 1, 2);
    insertElement(head, 2, 3);
    printf("Length: %d\n", length(head));
    printLinkedList(head);
    modifyElement(head, 1, 4);
    printLinkedList(head);
    insertElement(head, 1, 5);
    printLinkedList(head);
    deleteElement(head, 2);
    printLinkedList(head);
    destroyLinkedList(head);
    return 0;
}