I wouldn't feed just corn, calcium and grit. In fact, when it's mixed in with other seeds and grains, corn tends to be one of my chickens' least favorite foods. Also, it really warms them up. I give them more corn in the winter to help them keep warm, but if I fed them exclusively corn in the summer here in Arizona, they'd overheat fast!
Pellets are a great balance between good health and convenience, IMO. Our birds get good-quality pellets. BUT they also get lots of table scraps and are let out to free-range regularly. (Most outdoor flocks with a run don't need grit provided, by the way.)
Almost all animals do better on a varied diet. Veggies and grass, bugs, pellets, ground oystershell or eggshell for calcium, and table scraps are all part of a great diet for chickens. You can also give them dried mealworms or chicken scratch as a treat (NOT as a main course! For dessert!).
Alternatively, there are recipes out there for homemade chicken feed. Usually it is a mix of different kinds of grains -wheat, corn, barley, etc. -maybe with lentils, ground oystershell, and supplements mixed in. This is very tricky though, as you need to make sure your birds are getting the right amounts of protein, fat, and different nutrients. Sometimes we mix up some for our birds as a treat. I have also heard of different grains being sprouted as fodder for farm animals, including poultry. I've never done this. I'd imagine you'd still have to supplement with other foods for protein and calcium.
No matter what, the diet of the chickens should not be suddenly changed. For example, if you're giving pellets and want to switch to homemade, do your research on the best recipe and then switch over SLOWLY, over a period of weeks.
! Pleased you joined our community! You've already received a lot of great advice so I'll just say best wishes and thanks for joining BYC! 
Glad you joined the family. As already stated, you've gotten some good advice, I can't add to it so....Enjoy your time here
