-`std::ios_base::sync_with_stdio(false)`: by default, C++ works with C++ iostreams (like`std::cin`) and C style stdio streams (like`stdin`) by synchronizing them.

Since you should never need C style I/O (like`scanf`,`printf`), in C++, disabling this synchronization will make C++ I/O competitive with C style`scanf`.

-`std::cin.tie(0)`: By default, iostreams flush cout every time you read from cin, so that you will always display any output before reading any input.

If you are not solving an interactive problem, i.e. you don't require interleavinginputs and outputs, you candisable this automatic flushing to make I/O faster.

You can disable this automatic flushing to make I/O faster. The exception is for interactive problems with interleavedinputs and outputs,for whichyou caneither not use`cin.tie(0)` or flush explicitly with`cout.flush()`/`cout.endl`.

References:

[Dr. Dobbs - The Standard Librarian: IOStreams and Stdio](https://www.drdobbs.com/the-standard-librarian-iostreams-and-std/184401305),