operator==,!=(std::unordered_map) - cppreference.com (original) (raw)
| template< class Key, class T, class Hash, class KeyEqual, class Alloc > bool operator==( const std::unordered_map<Key, T, Hash, KeyEqual, Alloc>& lhs, const std::unordered_map<Key, T, Hash, KeyEqual, Alloc>& rhs ); | (1) | |
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| template< class Key, class T, class Hash, class KeyEqual, class Alloc > bool operator!=( const std::unordered_map<Key, T, Hash, KeyEqual, Alloc>& lhs, const std::unordered_map<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) |
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[edit] Parameters
| lhs, rhs | - | unordered containers to compare |
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[edit] Return value
true if the contents of the containers are equal, false otherwise.
true if the contents of the containers are not equal, false otherwise.
[edit] 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.