不带头结点的头插法和尾插法

可见：不带头指针的插入操作比较繁琐，尤其是尾插法，每次需要遍历链表找到尾节点，然后执行插入操作

typedef int DATA;struct SNode{DATA data;SNode *pNext;};SNode *g_pHead = NULL;/* 不带头结点的尾插法和头插法 */void AddHead(DATA d){SNode *p = (SNode *)malloc(sizeof(SNode));p->data = d;p->pNext = g_pHead; //新节点的后继g_pHead = p; //首结点}void  AddTail(DATA d){SNode *ptr = g_pHead;SNode *p = (SNode *)malloc(sizeof(SNode));p->data = d;p->pNext = NULL;if (!ptr) //第一次为空节点时{g_pHead = p;return;}while (ptr->pNext) //循环查找尾节点，然后插入{ptr = ptr->pNext;}ptr->pNext = p;}