It is a convenient way to charge your laptop, but it is not a safe one. You cannot charge it directly with a cigarette lighter, but you’ll use an inverter having 12V (voltage) to charge your laptop finely. You need to collect many things for this method, including an adapter, a charging cable, etc. Then a complete setup is necessary to charge your laptop computers in this way while driving. Try to adopt the 3 above-given methods that are the safest and most convenient as well.