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

template< class Key, class T, class Hash, class KeyEqual, class Allocator >
bool operator==( const unordered_map<Key,T,Hash,KeyEqual,Allocator>& lhs, 
                 const unordered_map<Key,T,Hash,KeyEqual,Allocator>& rhs );

template< class Key, class T, class Hash, class KeyEqual, class Allocator >
bool operator!=( const unordered_map<Key,T,Hash,KeyEqual,Allocator>& lhs, 
                 const unordered_map<Key,T,Hash,KeyEqual,Allocator>& rhs );

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).

Parameters

Return value

Complexity

Proportional to N 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, proportional to N² in the worst case where N is the size of the container.