How does hashing work in C++11 unordered maps?

Can you explain how hashing works in C++11 unordered maps?

Sure! In C++11, unordered maps use a hash function to map keys to buckets, allowing for average constant time complexity for lookups.

What is the default hash function used in unordered maps?

The default hash function is std::hash, which is specialized for various types like integers, strings, and pointers.

Can I use my own custom hash function?

Yes, you can provide a custom hash function by defining a struct or a function that implements the operator() for your key type.

What happens if two keys hash to the same bucket?

In that case, unordered maps handle collisions using chaining, where multiple elements are stored in a list within the same bucket.

Are there any performance considerations I should be aware of?

Yes, the choice of hash function and the load factor can significantly impact performance. A poor hash function can lead to many collisions.