[huhtenberg]

It would depend on the hardware used.

Standard counter-intuitive example (from the game development domain) is how to check if an array of integers has a zero in it. The answer, when all things are considered, is to scan through an entire array making a simple arithmetic for each item and one comparison at the end rather than compare each element.

The same may happen with your example. Filling up 32-bit mask might be more expensive than to flip an element in a boolean array. That's not even considering that the array option allows for early termination of the second loop.

[Oxryly]

Early termination is the biggest advantage of the array version. The 32-bit mask is probably the fastest possibility since it will reside in a register.