链栈的实现

#include<iostream>
using namespace std;
typedef struct StackNode *LinkStack;
struct StackNode {
    int data;
    struct StackNode *next;
};
LinkStack s;
void InitStack(LinkStack &s)
{
    s = NULL;
}
bool StackEmpty(LinkStack &s)
{
    if (s = NULL)
        return true;
    else
        return false;
}
void Push(LinkStack &s, int e)
{
    LinkStack p = new StackNode;
    if (!p)
    {
        cout << "error" << endl;
        return;
    }
    p->data = e;
    p->next = s;
    s = p;
}
void Pop(LinkStack &s, int &e)
{
    if (s == NULL)
    {
        cout << "error" << endl;
        return;
    }
    e = s->data;
    LinkStack p = s;
    s = s->next;
    delete p;
}
int GetTop(LinkStack &s)
{
    if (s == NULL)
    {
        cout << "error" << endl;
        return -1;
    }
    else
        return s->data;
}