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;}elsereturn 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;}