Nhap Xuat Sinh Vien Struct

#include <iostream>
#include <cstdio>

using namespace std;
struct Ngaythang
{
    int d, m, y;
};

struct Diem
{
    float dtoan, dly, dTB;
};
typedef struct Sinhvien
{
    char MaSV[30];
    char Hoten[30];
    Ngaythang ng;
    Diem d;
}SV;

void Nhap1SV(SV &x)
{
    cout << "Nhap MSSV: ";
    fflush(stdin);
    gets(x.MaSV);
    cout << "Nhap ho ten SV: ";
    fflush(stdin);
    gets(x.Hoten);
    cout << "Nhap ngay, thang, nam sinh: ";
    cin >> x.ng.d >> x.ng.m >> x.ng.y;
    float tam;
    cout << "Nhap diem toan: ";
    fflush(stdin);
    cin >> tam;
    x.d.dtoan = tam;
    cout << "Nhap diem ly: ";
    fflush(stdin);
    cin >> tam;
    x.d.dly = tam;
    x.d.dTB = (x.d.dtoan + x.d.dly)/2;
}
void Xuat1SV(SV x)
{
    cout << x.MaSV << endl;
    cout << x.Hoten << endl;
    cout << x.ng.d << "/" << x.ng.m << "/" << x.ng.y << endl;
    cout << x.d.dTB << endl;
}
void Nhapmang(SV a[], int &n)
{
    cout << "Nhap so phan tu cua mang: ";
    cin >> n;
    for (int i = 0; i < n; i++)
    {
        cout << "Nhap sinh vien thu " << i << endl;
        Nhap1SV(a[i]);
    }
}
void Xuatmang(SV a[], int n)
{
    for (int i = 0; i < n; i++)
    {
        Xuat1SV(a[i]);
    }
}
int maxxTBSV(SV a[], int n)
{
    float maxx = a[0].d.dTB;
    int vt;
    for (int i = 1; i < n; i++)
    {
        if (a[i].d.dTB > maxx)
        {
            maxx = a[i].d.dTB;
            vt = i;
        }
    }
    return vt;
}
int main()
{
    SV a[100];
    int n;
    Nhapmang(a, n);
    cout << "Danh sach sinh vien: " << endl;
    Xuatmang(a, n);
    int index = maxxTBSV(a, n);
    cout << "Sinh vien co diem trung binh cao nhat: " << endl;
    Xuat1SV(a[index]);
    return 0;
}