Question

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Is there a performance difference between i++ and ++i in C++?

I had an interview today and the interviewer asked me this question.

In C++ which is more “EFFICIENT” on non primitive types, A pre increment (++i) or a post increment (i++). I answered it by saying Pre increment but was not able to give the exact reason.

I have searched through the internet and found that Pre increment is more efficient. But I could not understand the reason. Can anyone please explain me the reason?

ex:

for ( ; c.value() != 21 ; ++c)
or
for ( ; c.value() != 21 ; c++)

Answer 1

pre-increment (++i) is usually faster since post-increment returns the current value and then increments the value, whereas pre-increment just increments the variable.

In many situations a compiler will optimise this anyway, unless you are using post-increment specifically to use the current value and increment the value afterwards.