Can anybody explain everything about the c++ code reference below?

Question

This is the cpp code to take fast input but i am not able to understand much about it how it is fast

https://code.sololearn.com/cMuadEfk4fqZ/?ref=app

then the normal io like this

https://code.sololearn.com/cIJQ1YPcJcW9/?ref=app

Thanks

Answer 1

why i was down voted?
Is there anything wrong in it?

Answer 2

@Deepak Gautam yeah it is not working here but working on my system. But i wanna know how it is fast compared to the normal one and want the explaination on it.