关于用链表方式实现对超市定价管理

#include<iostream>
#include<string>
using namespace std;
struct supermarket
{int num;string name;double price_trade;int pre_days;double price_retail;int count;supermarket *next;};
supermarket *creat(void);
void sum(supermarket *,int);
int n;
int main()
{
    char c;
    int number;
    bool prime=true;
    supermarket *head,*q;
    cout<<"calculate retail price(y).exit program(n)."<<endl;
    cin>>c;
    if(c=='y'|| c=='Y')
        head=creat();      
    else return 0;
    while(prime)
    {
        cin>>number;
        sum(head,number);
        cout<<"continue or not?"<<endl;
        cin>>c;
        if(c=='y'|| c=='Y')
            prime=true;
        else prime=false;
    }
    q=head;
    cout<<"商品的销售情况："<<endl;
    while(head!=0&&q!=0)
    {
        cout<<q->num<<' '<<q->name<<' '<<q->price_retail<<q->count;
        q=q->next;
    }
    return 0;
}

   
supermarket *creat(void)
{
    supermarket *head,*p1,*p2;
    n=0;
    p1=p2=new supermarket;
    cout<<"请输入各个商品的编号，名称，批发价，预售天数:"<<endl;
    cin>>p1->num>>p1->name>>p1->price_trade>>p1->pre_days;
    p1->price_retail=p1->price_trade+p1->pre_days/4;
    head=NULL;
    while(p1->num!=0)
    {
        n=n+1;
        if(n==1)
            head=p1;
        else p2->next=p1;
        p2=p1;
        p1=new supermarket;
        p1->price_retail=p1->price_trade+p1->pre_days/4;
    }
    p2->next=NULL;
    return head;
}

void sum(supermarket *head,int n)
{
    supermarket *p;  
    p=head;
    p->count=0;
    if(head!=NULL)
        while(p!=NULL)
        {
            if(p->num==n)
            {p->count=p->count+1;break;}
             p=p->next;
        }
}
编译没问题，但是运行不出结果，求指教！