//创建链表void Creat_Link_List(point **head, int l){    point *p, *q;//p为指向最末端的指针（最末端指next = NULL），q为构建链表的新变量，看下面就知道    int i;//i为循环变量    p = (point *)malloc(sizeof(point));    p->next = NULL;                                    //链表初始化：置空S    for (i = 0; i <= l; i++)//i <= l因为，头节点不算在链表长度内    {        q = (point *)malloc(sizeof(point));        q->x = 0;        q->next = NULL;        if ((*head)->next == NULL)        {            (*head)->next = q;            p = q;        }        else        {            p->next = q;            p = q;        }    }}