I have this enum:
enum ButtonState {
BUTTON_NORMAL = 0,
BUTTON_PRESSED = 1,
BUTTON_CLICKED = 2
};
const u8 NUM_BUTTON_STATES = 3;
It is perfectly normal to use an enum for indexing into an array.
You don't have to specify each enum value, they will increment automatically by 1. Letting the compiler pick the values reduces the possibility of mistyping and creating a bug, but it deprives you of seeing the values, which might be useful in debugging.