# std::unordered_map::at

 T& at( const Key& key ); (1) (since C++11) const T& at( const Key& key ) const; (2) (since C++11)

Returns a reference to the mapped value of the element with key equivalent to key. If no such element exists, an exception of type std::out_of_range is thrown.

## Contents

### Parameters

 key - the key of the element to find

### Return value

Reference to the mapped value of the requested element

### Exceptions

std::out_of_range if the container does not have an element with the specified key

### Complexity

Average case: constant, worst case: linear in size.