fast io

To implement fast input/output (I/O) in C++, you can follow the steps below:

Include the necessary headers: Begin by including the required C++ libraries for input/output operations. This is typically done by including the <iostream> header.
Disable synchronization with C I/O functions: To speed up the I/O operations, you can disable the synchronization between the C++ and C I/O functions. This can be done using the std::ios_base::sync_with_stdio(false); statement.
Tie C++ streams with C I/O streams: By default, the C++ input/output streams (std::cin and std::cout) are synchronized with the C I/O streams (stdin and stdout). However, for faster I/O, you can untie the C++ streams from the C I/O streams using the std::cin.tie(nullptr); statement.
Optimize buffer flushing: By default, the C++ streams flush the buffer after every newline character (\n). This can be inefficient for fast I/O. To disable automatic buffer flushing, you can use the std::cout.tie(nullptr); statement.
Use optimized I/O functions: Instead of using the standard input/output functions (std::cin and std::cout), you can use their optimized counterparts, std::scanf and std::printf, for faster I/O. These functions have a different syntax and provide faster I/O operations.
Avoid unnecessary function calls: Minimize the number of function calls when performing I/O operations. Each function call has an overhead, so reducing unnecessary calls can improve the overall speed.

It's important to note that fast I/O techniques are generally used in competitive programming or situations where the input/output size is large, and performance is crucial. However, in most normal scenarios, the standard I/O functions provided by C++ are sufficient and efficient.

I hope this explanation helps! Let me know if you have any further questions.