结构之创建链表的小问题

[MZJCDD]

#include<iostream.h>
typedef struct student
{int num;
struct student *next;
}M;



M *creat()
{M *head,*ps,*pend;
head=NULL;
ps=new M;
cin>>ps->num;
pend=ps;
while(ps->num>0)
{if(head==NULL)
head=ps;
else
pend->next=ps;//把ps所指向的接点连接到表末
pend=ps;//第一次时候这句和第九行的那句重复了，但是为了和以后的链表连接这句是必要的
ps=new M;
cin>>ps->num;

}
pend->next=NULL;
delete ps;
return(head);
}
void showlist(M *head)
{
cout<<"now the items of list \n";
while(head);
{cout<<head->num<<" ";
head=head->next;
}

}

void main()
{showlist(creat());
}
这是c++里面的创建和输出链表的程序！为什么运行不出来结果啊！请高手指点！！！！！

[effective_person]

#include <iostream.h> 
typedef struct student 
{
	int num; 
	struct student *next; 
}M; 
M *creat() 
{
	M *head,*ps,*pend; 
	head=NULL; 
	ps=new M; 
	cin>>ps->num; 
	pend=ps; 
	while(ps->num>0) 
	{
		if(head==NULL) 
			head=ps;
		else 
			pend->next=ps;//把ps所指向的接点连接到表末 
		pend=ps;//第一次时候这句和第九行的那句重复了，但是为了和以后的链表连接这句是必要的 
		ps=new M; 
		ps->next=NULL;
		cin>>ps->num; 
	} 
	pend->next=NULL; //here 
	delete ps; 
  return head; 
} 
void showlist(M *head) 
{ 
	cout <<"now the items of list \n"; 
	while(head) // here 多了；
	{
		cout <<head->num <<" "; 
		head=head->next; 
	}  
} 

void main() 
{
	showlist(creat()); // 
}