"faster" is true; "more effective" depends on the desired effect. Depending on your stdout, the behavior of the two is different, since endl forces a buffer flush.

Clever

love the readbility but this isnt the best way

Clever.

So, this is not the best practice even though it has 68 best practices. This mean I should not just beleive this counter, I think.

I have just joined codewars and want to understand it.

Yes, and while doing this it builds three potentially unnecessary intermediate strings.

Tell me please, does this solution iterate over formData four times?

While it was fun to figure out the one-liner, this is far more readable

Yo!

If you want to compare these 2 printing methods, do it yourself - removing << "\n" from "Hello cout" << "\n" reduces the number of assembly commands from 10 to 4, just 1 more than with printf, and puts is in face just 2 assembly commands - 1 less than printf.

This is not the most efficient option.

This is the most efficient solution.

better use stringbuffer or stringdtreamer