std::unordered_map include

To use std::unordered_map in C++, you need to include the <unordered_map> header file in your code. This header file defines the unordered_map template class and its associated functions and types. Here is an example of how to include it:

#include <unordered_map>

Once you have included this header file, you can start using the std::unordered_map class in your code.