What are some effective hash functions for unordered maps in C++?

What are some effective hash functions for unordered maps in C++?

In C++, unordered maps use hash functions to efficiently store and retrieve key-value pairs. Some effective hash functions include std::hash, custom hash functions, and those from libraries like Boost.

Can you explain how std::hash works?

Sure! std::hash is a template class in C++ that provides a default hash function for various types. It generates a hash value based on the input, which helps in distributing keys uniformly in the unordered map.

What are the benefits of using custom hash functions?

Custom hash functions can improve performance by reducing collisions for specific data types or distributions, leading to faster access times.

Are there any common pitfalls when using hash functions?

Yes, common pitfalls include poor hash function design leading to collisions, not handling all possible input types, and not considering the load factor of the unordered map.