Pretty sure that modern compilers will optimise this away, as long as the length of the string isn't changed in the loop (or declaired as volatile).

This JavaScript solution sometimes does not pass a random test.

Well, that was painfull. Not a huge fan of traps like this, but lesson learned.

SOLVED: Apparently there was an off-by-one error in the for loop reversing the words. This led to undefined chars being appended at the front of each word (probably null bytes). It seems like std::cout ignores null bytes, as it uses the length of the container class std::string to terminate that string, therefore printing it correctly.