Sweetpotatoes have more potassium than banannas. Additional calcium is also helpful for muscle cramps. Be certain that you are very well hydrated and include things like Pedialyte, Gatorade, or similar rehydration formulas as well as plain water to maintain good electrolyte balance if you've been exposed to extreme heat and sweating a lot.
Cramps are, to some extent, normal during pregnancy. A warning though -- my blood clot in my 3rd pregnancy started out feeling just exactly like a bad muscle cramp. So if the cramp does not go away or if it partially fades then comes back over and over be sure to have that possibility evaluated.
I didn't know any better and let it get to a very dangerous stage before I saw the doctor. But now you do know and if it happens you can catch it BEFORE its bad enough to require 10 days in the hospital.