operator==,!=(std::unordered_multimap)

 

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std::unordered_multimap

Member types
Member functions
unordered_multimap::unordered_multimap unordered_multimap::~unordered_multimap    unordered_multimap::operator= unordered_multimap::get_allocator Iterators unordered_multimap::beginunordered_multimap::cbegin unordered_multimap::endunordered_multimap::cend Capacity unordered_multimap::size unordered_multimap::max_size unordered_multimap::empty Modifiers unordered_multimap::clear unordered_multimap::insert unordered_multimap::insert_range (C++23) unordered_multimap::emplace unordered_multimap::emplace_hint unordered_multimap::erase unordered_multimap::swap unordered_multimap::extract (C++17) unordered_multimap::merge (C++17)	Lookup unordered_multimap::count unordered_multimap::find unordered_multimap::contains (C++20) unordered_multimap::equal_range Bucket interface unordered_multimap::begin(size_type)unordered_multimap::cbegin(size_type) unordered_multimap::end(size_type)unordered_multimap::cend(size_type) unordered_multimap::bucket_count unordered_multimap::max_bucket_count unordered_multimap::bucket_size unordered_multimap::bucket Hash policy unordered_multimap::load_factor unordered_multimap::max_load_factor unordered_multimap::rehash unordered_multimap::reserve Observers unordered_multimap::hash_function unordered_multimap::key_eq
Non-member functions
std::swap(std::unordered_multimap) erase_if(std::unordered_multimap) (C++20)	operator==operator!= (until C++20)
Deduction guides (C++17)

 

template< class Key, class T, class Hash, class KeyEqual, class Alloc > bool operator==( const std::unordered_multimap<Key, T, Hash, KeyEqual, Alloc>& lhs,                  const std::unordered_multimap<Key, T, Hash, KeyEqual, Alloc>& rhs );	(1)
template< class Key, class T, class Hash, class KeyEqual, class Alloc > bool operator!=( const std::unordered_multimap<Key, T, Hash, KeyEqual, Alloc>& lhs,                  const std::unordered_multimap<Key, T, Hash, KeyEqual, Alloc>& rhs );	(2)	(until C++20)

Compares the contents of two unordered containers.

The contents of two unordered containers lhs and rhs are equal if the following conditions hold:

• lhs.size() == rhs.size().
• each group of equivalent elements [lhs_eq1, lhs_eq2) obtained from lhs.equal_range(lhs_eq1) has a corresponding group of equivalent elements in the other container [rhs_eq1, rhs_eq2) obtained from rhs.equal_range(rhs_eq1), that has the following properties:

• std::distance(lhs_eq1, lhs_eq2) == std::distance(rhs_eq1, rhs_eq2).
• std::is_permutation(lhs_eq1, lhs_eq2, rhs_eq1) == true.

The behavior is undefined if Key or T are not EqualityComparable.

The behavior is also undefined if hash_function() and key_eq() do(until C++20)key_eq() does(since C++20) not have the same behavior on lhs and rhs or if operator== for Key is not a refinement of the partition into equivalent-key groups introduced by key_eq() (that is, if two elements that compare equal using operator== fall into different partitions).

The != operator is synthesized from operator==.

(since C++20)

Parameters

lhs, rhs

-

unordered containers to compare

Return value

1) true if the contents of the containers are equal, false otherwise.

2) true if the contents of the containers are not equal, false otherwise.

Complexity

Proportional to ΣS_i² calls to operator== on value_type, calls to the predicate returned by key_eq, and calls to the hasher returned by hash_function in the average case, where S is the size of the ith equivalent key group. Proportional to N² in the worst case, where N is the size of the container. Average case becomes proportional to N if the elements within each equivalent key group are arranged in the same order (happens when the containers are copies of each other).