单链表逆序的三种方法

一、不使用额外存储空间的逆序

LinkList ReverseLink(LinkList L)
{
    LinkList *next;
    LinkList *prev = NULL;
    LinkList *head = L->next;

    while(head != NULL)
    {
        next = head->next;
        head->next = prev;
        prev = head;
        head = next;
    }

    L->next = prev
    return L;
}

二、头插法逆序

LinkList ListReverse(LinkList L)
{
    LinkList current,pnext,prev;
    if(L == NULL || L->next == NULL)
        return L;
    current = L->next;  /* p1指向链表头节点的下一个节点 */
    pnext = current->next;
    current->next = NULL; /* 断开链表 */
    while(pnext)
    {
        prev = pnext->next;
        pnext->next = current;
        current = pnext;
        pnext = prev;
        printf("交换后：current = %d,next = %d \n",current->data,current->next->data);
    }
    L->next = current;  /* 将链表头节点指向p1 */
    return L;
}

三、递归逆序

/*链表的逆序*/
Node* reverse_list(Node *plist, Node *&head) //这个函数的返回值并不是最终链表逆序后的链表头，而是尾，
                                            //它的头保存在head指针里，所以head用的是指针引用.
{
    Node *pback = NULL;
    if(plist == NULL || plist->next == NULL)
    {
        head->next = plist;
        return plist;
    }
    else
    {
        pback = reverse_list(plist->next, head);
        pback->next = plist;
        return plist;
    }
}