In ra tam giác cân ngược rỗng

// In ra tam giac can nguoc rong ruot
// Khai bao chuong trinh nhu sau
#include <iostream.h>

void main()
{
    int n;
    cout <<"Nhap kich thuoc tam giac: "; cin>>n;
    cout <<"\n\n";

    int a=(2*n-1);
    int b=(a /2+1);

    for (int i=1;i<=n;i++)
    {
        for (int j=1;j<=a;j++)
        {
            if (i==1)
            {
                if ((j%2)!=0) cout <<"*";
                else cout <<" ";
            }
            else if ((j==i) || (j==a+1-i)) cout <<"*";
            else cout <<" ";

        }
        cout <<"\n";
    }

    cout <<"\n\n";
}