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()
[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 | (since C++20) |
lhs, rhs | - | unordered containers to compare |
true
if the contents of the containers are equal, false
otherwisetrue
if the contents of the containers are not equal, false
otherwiseProportional to ΣS_{i}^{2} 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 N^{2} 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).
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
https://en.cppreference.com/w/cpp/container/unordered_multimap/operator_cmp