c++中关于结构数组的问题

#include
using namespace std;
struct Data
{ int n;
double score;
};
int main()
{ Data a[3] = { 1001,87,1002,72,1003,90 }, *p = a;
cout << (p++)->n << endl;
cout << (p++)->n << endl;
cout << p->n++ << endl;
cout << (*p).n++ << endl;
}
四个cout有什么区别吗
1001
1002
1003
1004