IS it wrong to leave out some dry food for neighborhood cats?

My neighbor has a cat that is outside all of the time. Rain, Snow , 20 degrees outside and the cat is out, I dont think they ever let it in. It was on my patio one cold day looking in at my cats and felt bad for it and out out a little saucer of dry food, and I have continued to put a little out there when ever he eats it all, is this wrong - what would you do?