链栈的实现 c++

#include <iostream>
#include <string>
using namespace std;

struct Data
{
public:
int bookNum;
Data * next;
};
//栈的初始化
Data* SeqStackInit()
{
Data *top = new Data;
top = NULL;
return top;
}

//栈的判空
int SeqStackEmpty(Data* s)
{
if (NULL == s)
{
return true;
}
else
return false;

}

//栈的入栈
Data * SeqStackPush(Data* s, int x)
{
Data* s1 = new Data;
s1->bookNum = x;
s1->next = s;
s = s1;
cout<<"入栈元素："<<s->bookNum<<endl;
return s;
}

//栈的出栈
Data * SeqStackPop(Data* s)
{
if (NULL != s)
{
int x;
Data * p = new Data;
p =	s;
x = s->bookNum;
cout <<"出栈元素："<<s->bookNum<<endl;
s = s->next;
delete(p);
return s;
}
}

//栈中取出栈顶元素
int SeqStackGetTop(Data* s)
{
if (NULL != s)
return s->bookNum;
}

//栈的长度
int SeqStackLength(Data* s)
{
int length = 0;
Data* s1 = s;
//cout <<s->bookNum<<endl;
while(NULL != s1)
{
length++;
s1 = s1->next;
}
return length;

}
int main()
{
Data* s = SeqStackInit();
cout <<"判空操作："<<SeqStackEmpty(s)<<endl;
cout <<"入栈操作："<<endl;
s = SeqStackPush(s,12);
s = SeqStackPush(s,23);
s = SeqStackPush(s,4);
s = SeqStackPush(s,78);
s = SeqStackPush(s,3);
cout <<"栈顶元素："<<SeqStackGetTop(s)<<endl;
cout <<"栈的长度："<<SeqStackLength(s)<<endl;
cout <<"出栈操作："<<endl;
s = SeqStackPop(s);
cout <<"判空操作："<<SeqStackEmpty(s)<<endl;
cout <<"栈的长度："<<SeqStackLength(s)<<endl;
cout <<"栈顶元素："<<SeqStackGetTop(s)<<endl;
return 0;
}