CTDL&TT: Sắp xếp Hậu

#include<iostream>
#include<math.h>
using namespace std;

int a[20];
int count;

bool Ok(int x2,int y2){
    for(int i = 1; i < x2 ;i++)
        if(a[i] == y2 || abs(i-x2) == abs(a[i] - y2) )
            return false;
    return true;
}

void Xuat(int n){
    cout << endl << ++count << ":  ";
    for(int i = 1;i <= n;i++)
        cout << a[i] << " ";
    cout << endl;
}

void Try(int i,int n){
    for(int j = 1;j <= n;j++){
        if(Ok(i,j)){
            a[i] = j;
            if(i == n) Xuat(n);
            Try(i+1,n);
        }
    }
}

int main(){
    cout << "Nhap n: ";
    int n;
    cin >> n;
    cout << endl << "----- Cac cach sap xep: ----- " << endl;
    Try(1,n);
    if (count == 0) cout << "----- Khong co cach sap xep nao! -----" << endl;
    cout << endl << "---- Co " << count << " cach sap xep cac con hau! ----" << endl;
    return 0;
}