++p is usually faster than p++ and --p is faster than p--, especially for objects of types with overloaded prefix and postfix increment and decrement operators, because prefix form just increments or decrements something and returns the new value, whereas the postfix form increments or decrements something, but has to keep the old value somewhere to return it. That is, instead of (replace int with your favorite class here)
for ( int i ( 0); i < x; i++)
always write
for ( int i ( 0); i < x; ++i)
