# Unordered Associative
[Containers]

Collaboration diagram for Unordered Associative:

## Classes

- class std::unordered_map< _Key, _Tp, _Hash, _Pred, _Alloc >
    A standard container composed of unique keys (containing at most one of each key value) that associates values of another type with the keys. More...
- class std::unordered_multimap< _Key, _Tp, _Hash, _Pred, _Alloc >
    A standard container composed of equivalent keys (possibly containing multiple of each key value) that associates values of another type with the keys. More...
- class std::unordered_multiset< _Value, _Hash, _Pred, _Alloc >
    A standard container composed of equivalent keys (possibly containing multiple of each key value) in which the elements' keys are the elements themselves. More...
- class std::unordered_set< _Value, _Hash, _Pred, _Alloc >
    A standard container composed of unique keys (containing at most one of each key value) in which the elements' keys are the elements themselves. More...

## Detailed Description

Unordered associative containers allow fast retrieval of data based on keys.

Each container type is parameterized on a `Key` type, a `Hash` type providing a hashing functor, and an ordering relation used to sort the elements of the container.

All unordered associative containers must meet certain requirements, summarized in tables.