请找出错误

#include <iostream>
#include <string.h>

using namespace std;

typedef struct Student{
int num;
string name;
char sex[12];
float score;
} Student;

int main()
{
Student stu;
cout<<"num is ";
cin>>stu.num;
cout<<"name is ";
char str[256];
cin>>str;
stu.name=str;
cout<<"sex is ";
cin>>stu.sex;
cout<<"score is ";
cin>>stu.score;

cout<<stu.num<<"\t"<<stu.name.c_str()<<"\t"<<stu.sex<<"\t"<<stu.score<<endl;
return 0;
}

#define NULL 0
#include<iostream>
using namespace std;

typedef struct Student
{
long num;
float score;
Student *next;
} Student;

int main()
{
Student a,b,c,*head,*p;
a.num=31001;a.score=39.5;
b.num=31003;b.score=90;
c.num=31007;c.score=85;
head=&a;
a.next=&b;
b.next=&c;
c.next=NULL;
p=head;
do
{
cout<<p->num<<" "<<p->score<<endl;
}
while ((p=p->next) != NULL);

return 0;
}