大一上学期的一点小疑惑，代码验证ok

#include<iostream>
using namespace std;
class test
{
    int *p;
    int pn;
public:
    test(int n) { p = new int[n]; pn = n; }
    void setp();
    int* getp() { return p; }
    int getpn() { return pn; }
};
void test::setp()
{
    int choice;
    cout << "1:自动填充
2:手动填充" << endl;
    cin >> choice;
    switch (choice)
    {
    case 1:
        for (int i = 0; i < pn; i++)
            p[i] = i;
        break;
    case 2:
        for (int i = 0; i < pn; i++)
            cin>>i;
        break;
    }
}
void main()
{
    test A(4);
    A.setp();
    int*b = new int[A.getpn()];
    b = A.getp();
    for (int i = 0; i < A.getpn(); i++)
        cout << b[i] << endl;
}