#include <iostream>
#include <conio.h>
using namespace std;
struct NgaySinh
{
	int d, m, y;
};
struct HocSinh
{
	char Ten[25];
	float DTB;
	float Toan, Ly, Hoa;
	NgaySinh NS;
};
void NhapNgaySinh(NgaySinh &NS)
{
	cout << "Ngay : ";
	cin >> NS.d;
	cout << "Thang: ";
	cin >> NS.m;
	cout << "Nam  : ";
	cin >> NS.y;
	fflush(stdin);
	if (NS.d < 0 || NS.d > 31)
	{
		cout << "ERROR";
		NhapNgaySinh(NS);
	}
	else
	{
		if (NS.m == 4 || NS.m == 6 || NS.m == 9 || NS.m == 11)
		{
			if (NS.d == 31)
			{
				cout << "ERROR";
				NhapNgaySinh(NS);
			}
		}
		if (NS.m == 2)
		{
			if (NS.y % 4 == 0 && NS.y % 100 != 0)
			{
				if (NS.d > 29)
				{
					cout << "ERROR";
					NhapNgaySinh(NS);
				}
			}
			else
			{
				if (NS.y % 400 == 0)
				{
					if (NS.d > 29)
					{
						cout << "ERROR";
						NhapNgaySinh(NS);
					}
				}
			}
		}
	}
}
void XuatNgaySinh(NgaySinh NS)
{
	cout << "Ngay : " << NS.d << endl;
	cout << "Thang: " << NS.m << endl;
	cout << "Nam  : " << NS.y << endl;
}
void NhapThongTin(HocSinh &Hs)
{
	fflush(stdin);
	cout << "Nhap Ten: ";
	cin.getline(Hs.Ten, 25);
	do
	{
		cout << "Toan: ";
		cin >> Hs.Toan;
	} while (Hs.Toan < 0.0 || Hs.Toan > 10.0);
	do
	{
		cout << "Ly  : ";
		cin >> Hs.Ly;
	} while (Hs.Ly < 0.0 || Hs.Ly > 10.0);
	do
	{
		cout << "Hoa : ";
		cin >> Hs.Hoa;
	} while (Hs.Hoa < 0.0 || Hs.Hoa > 10.0);
	Hs.DTB = (Hs.Toan * 2 + Hs.Ly + Hs.Hoa) / 4;
	fflush(stdin);
	NhapNgaySinh(Hs.NS);
}
void XuatThongTin(HocSinh &Hs)
{
	cout << "Ten : " << Hs.Ten << endl;
	cout << "Toan: " << Hs.Toan << endl;
	cout << "Ly  : " << Hs.Ly << endl;
	cout << "Hoa : " << Hs.Hoa << endl;
	cout << "DTB : " << Hs.DTB << endl;
	XuatNgaySinh(Hs.NS);
}
void NhapDanhSach(HocSinh *Hs, int n)
{
	for (int i = 0; i < n; i++)
		NhapThongTin(Hs[i]);
}
void XuatDanhSach(HocSinh *Hs, int n)
{
	for (int i = 0; i < n; i++)
		XuatThongTin(Hs[i]);
}
void Swap(HocSinh &a, HocSinh &b)
{
	HocSinh t;
	t = a;
	a = b;
	b = t;
}
void QuickSort(HocSinh Hs[], int l, int r)
{
	int i = l, j = r;
	float x = Hs[(i + j) / 2].DTB;
	do
	{
		while (Hs[i].DTB > x) i++;
		while (Hs[j].DTB < x) j--;
		if (i <= j)
		{
			Swap(Hs[i], Hs[j]);
			i++;
			j--;
		}
	} while (i <= j);
	if (i < r) QuickSort(Hs, i, r);
	if (j > l) QuickSort(Hs, l, j);
}
void main()
{
	int n;
	HocSinh *Hs = NULL;
	cout << "So sinh vien can nhap: ";
	cin >> n;
	Hs = new HocSinh[n];
	NhapDanhSach(Hs, n);
	QuickSort(Hs, 0, n - 1);
	int luachon;
	do
	{
		system("cls");
		cout << "1. Sap xep theo diem trung binh\n2. Danh sach nguoi co DTB < 5.0";
		luachon = getch();
		luachon -= 48;
		switch (luachon)
		{
		case 1:
			XuatDanhSach(Hs, n);
			break;
		case 2:
			for (int i = n - 1; i >= 0; i--)
			{
				if (Hs[i].DTB < 5.0) XuatThongTin(Hs[i]);
				else break;
			}
			break;
		default:
			break;
		}
	} while (luachon != 1 || luachon != 2);
	delete[] Hs;
}