数据结构的作业，将一个链式堆栈里的元素倒置，不知道怎么就是报错

#include<iostream>
using namespace std;

typedef struct Lnode {               //链表节点
    int data;
    Lnode *next;
}Lnode;

class Llist {                        //链表类
private:
    Lnode *head, *tail;
public:
    Llist(int x);
    void ReverseLinkList();
    void show();
};
Llist::Llist(int x) {
    Lnode *nitem;
    head = new Lnode;
    head->next = NULL;
    tail = head;
    for (int i = 1; i <= x; i++) {
        nitem = new Lnode();
        nitem->data = i;
        tail->next = nitem;
        tail = nitem;
    }
}
void Llist::show() {
    Lnode *p = head->next;
    while (p != NULL) {
        cout << p->data << " ";
        p = p->next;
    }
    cout << endl;
}
void Llist::ReverseLinkList() {                    //将第一个节点提取出来插入尾部，直到原本的尾节点为止
    if (head->next = NULL) {
        cout << "链表为空" << endl; return;
    }
    Lnode *tem = head->next, *ptail = tail;
    while (tem != ptail) {
        getchar();
        head->next = tem->next;
        tail->next = tem;
        tail = tem;
        tem = head->next;
    }
}

int main()
{
    Llist L1(5);
    L1.show();

    L1.ReverseLinkList();
    L1.show();

    return 0;
}
求救！

谢谢！你不说我还没发现有问题