//Tim tat cac cac phan so co mau la x
public MangPhanSo TimPhanSoCoMauLa(int x)
{
MangPhanSo kq = new MangPhanSo();
for (int i = 0; i < len; i++)
{
if (a[i].mau == x)
{
kq.Chen(a[i]);
}
}
return(kq);
}
