Yes, get the correct adapter for your model of computer, I have one that works for my mac.
The amount of energy to charge your laptop once won't affect starting the car. But if you expect to charge your laptop 50 times before starting and running the engine, then the outcome may well be different.
You can buy a small 100 Watt inverter that converts 12VDC to 110VAC and plug your laptop adapter in as you would in a normal 110V outlet at home. The inverter itself plugs into the cigarette lighter/12V power outlet. You can not only charge the battery when the engine is running. You can also the laptop when you at a rest area or truck stop.
I bought my inverter at a truck stop for around $20.00 Most of these inverters also a USB connector for 5VDC to charge a cell phone or tablet.