fast io c++

Fast I/O in C++ is a technique used to optimize input/output operations, making them faster compared to the standard methods provided by C++. It involves using different functions and techniques to minimize the time taken for input/output operations.

Here are the steps to implement fast I/O in C++:

  1. Disable synchronization with stdio: By default, C++ synchronizes the C++ standard streams (like cin, cout) with the C standard streams (like scanf, printf). Synchronization can cause a performance overhead, so it is recommended to disable it. You can disable synchronization by adding the following line at the beginning of your code: cpp std::ios_base::sync_with_stdio(false);

  2. Untie cin and cout: The cin and cout objects are tied by default, meaning that when you perform an input operation, the output buffer is flushed first. Untying them can improve performance. You can untie cin and cout by adding the following line after disabling synchronization: cpp std::cin.tie(nullptr);

  3. Use a faster input function: The standard method to read input in C++ is through the cin stream, but it can be slower compared to other techniques. One faster alternative is the scanf function from the C library. To use scanf in C++, you need to include the cstdio header and use the following code: cpp #include <cstdio> // ... int x; scanf("%d", &x);

  4. Use a faster output function: Similarly, the standard method to write output in C++ is through the cout stream, but it can be slower compared to other techniques. One faster alternative is the printf function from the C library. To use printf in C++, you need to include the cstdio header and use the following code: cpp #include <cstdio> // ... int x = 42; printf("%d\n", x);

By following these steps, you can optimize input/output operations in C++ and achieve faster execution times for your programs.