If you don't want to branch you could do something like this:
NSString *myString = myArray[(NSUInteger)ceil((double)(intptr_t)(__bridge void *)object / ((double)(intptr_t)(__bridge void *)object + 1))];
There is probably a better way than this, but I can't think right now. It shows the idea though.
Actually, having thought about this the following will work and be more readable:
myArray[(intptr_t)(__bridge void *)object && 1];
Branching isn't that bad though, unless there are specific reasons why you want to avoid branching.