【C语言】带头节点的链表的增删

#include 

typedef struct grade
{
    int score;
    struct grade *next;
}NODE;


NODE *list_creat();
int list_insert(NODE* head,NODE *pNew);
int list_delete_item(NODE *list,NODE *item);
void list_destory(NODE *list);
void showList(NODE *head);

void showList(NODE *head)
{
    NODE *p =NULL;
    for(p = head->next;p!=NULL;p = p->next)
    {
        printf("%d ",p->score);
    }
    printf("n");
}
void list_destory(NODE *list)
{
  
    NODE *delete = NULL;
    while(NULL != list->next)
    {
        delete = list->next;
        list->next = delete->next;
        free(delete);
    }
    free(list);
}
NODE *list_creat()
{
    NODE *head = NULL;
    NODE *tail = NULL;
    int score = 0;
    //带头节点的链表创建:  头节点的数据域不能有值， 
    head = (NODE*)malloc(sizeof(NODE));
    if(NULL == head)
    {
        return NULL;
    }
    head->next = NULL;
    tail = head;
    
    NODE *pNew = NULL;

    pNew = (NODE *)malloc(sizeof(NODE));
    if(NULL == pNew)
    {
        return NULL;
    }

    score = 99;

    pNew->score = score;
    pNew->next = NULL;
    tail->next = pNew;
    tail = pNew;

    return head;
}
int list_insert_tail(NODE* list,NODE *pNew)
{
  
    NODE *last = list->next;

    while(last)
    {
        if(last->next == NULL)
        {
            pNew->next = last->next;
            last->next = pNew;
            break;
        }
        last = last->next;
    }



}
int list_insert(NODE* head,NODE *pNew)
{
    //带头节点的头插法
    pNew->next = head->next;
    head->next = pNew;

    return 0;
}
int list_delete_item(NODE *list,NODE *item)
{
    NODE *head = list;

    if(item == head)
    {
        head->next = item->next;
        return ;
    }

    while(head)
    {   
        if(item == head->next)
        {
            break;
        }
        head = head->next;
    }
    if(head)
    {
        head->next = item->next;
    }
    free(item);
    return 0;
}

int main()
{
    printf("list test:n");
    NODE *new_node = NULL;
    NODE *new_node1 = NULL;
    NODE *list = NULL;
    list = list_creat();
    printf("one node :");
    showList(list);
    new_node = (NODE *)malloc(sizeof(NODE));
    if(NULL == new_node)
    {
        return -1;
    }
    new_node ->score= 100;

    list_insert(list,new_node);
    printf("one and two node:");
    showList(list);
    new_node1 = (NODE *)malloc(sizeof(NODE));
    if(NULL == new_node1)
    {
        return -1;
    }
    new_node1->score= 98;
    //list_insert(list,new_node1);   //头插
    list_insert_tail(list,new_node1);   //尾插
    printf("All the nodes :");
    showList(list);
    list_delete_item(list,new_node1); //删除节点
    printf("after delete third node :");
    showList(list);
    list_destory(list);
    return 0;
}