std::multimap<Key,T,Compare,Allocator>::equal_range
equal_range( const Key& key ) const;
std::pair <iterator, iterator> equal_range( const K& x );
(constexpr since C++26)
std::pair <const_iterator, const_iterator>
(constexpr since C++26)
Returns a range containing all elements with the given key in the container. The range is defined by two iterators, one pointing to the first element that is not less than the given key and another pointing to the first element greater than the given key.
Alternatively, the first iterator may be obtained with lower_bound() , and the second with upper_bound() .
Compare is transparent. It allows calling this function without constructing an instance of Key.[edit] Parameters
Key
[edit] Return value
std::pair containing a pair of iterators defining the wanted range:
- The first iterator points to the first element not less than the given key, or end() if no such element exists.
- The second iterator points to the first element greater than the given key, or end() if no such element exists.
Since emplace and unhinted insert always insert at the upper bound, the order of equivalent elements in the equal range is the order of insertion unless hinted insert or emplace_hint was used to insert an element at a different position.
[edit] Complexity
Logarithmic in the size of the container.
Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_generic_associative_lookup |
201304L |
(C++14) | Heterogeneous comparison lookup in associative containers, for overloads (3,4) |
[edit] Example
#include <iostream> #include <map> int main() { std::multimap <int, char> dict { {1, 'A'}, {2, 'B'}, {2, 'C'}, {2, 'D'}, {4, 'E'}, {3, 'F'} }; auto range = dict.equal_range(2); for (auto i = range.first; i != range.second; ++i) std::cout << i->first << ": " << i->second << '\n'; }
Output:
2: B 2: C 2: D
[edit] See also
(public member function) [edit]