make cin cout faster

To make cin and cout faster in C++, you can use the following techniques:

1. Disable synchronization with C I/O functions: By default, cin and cout are synchronized with the C I/O functions (stdio). This means that when you read from or write to cin or cout, the corresponding C I/O functions are also called, which can slow down the process. You can disable this synchronization to make cin and cout faster by adding the following lines of code at the beginning of your program:

std::ios::sync_with_stdio(false);
std::cin.tie(nullptr);

The std::ios::sync_with_stdio(false) line disables the synchronization between iostream and stdio, and std::cin.tie(nullptr) unties cin from cout, which further improves the performance.

2. Use a larger buffer size: By default, cin and cout use a small buffer size for input and output operations. You can increase the buffer size to reduce the number of system calls, which can improve the performance. You can do this by calling the rdbuf() function on cin and cout and setting a larger buffer size. For example:

std::cout.rdbuf(std::cout.rdbuf()->pubsetbuf(nullptr, 0));
std::cin.rdbuf(std::cin.rdbuf()->pubsetbuf(nullptr, 0));

The pubsetbuf function sets the buffer to nullptr and the size to 0, which lets the stream library choose an appropriate buffer size.

3. Avoid unnecessary calls to endl: The endl manipulator in C++ is equivalent to '\n' and also flushes the output buffer. Calling endl frequently can slow down the output operation. Instead, you can use '\n' to insert a newline character without flushing the buffer, unless you explicitly need to flush the buffer.

By applying these techniques, you can make cin and cout faster in your C++ programs. Remember to test the performance gain after making these changes, as the actual impact may vary depending on the specific program and system configuration.