public member function
pair<const_iterator,const_iterator> equal_range (const key_type& k) const;pair<iterator,iterator> equal_range (const key_type& k);
Get range of equal elements
Returns the bounds of a range that includes all the elements in the container which have a key equivalent to k.
Because the elements in a map container have unique keys, the range returned will contain a single element at most.
If no matches are found, the range returned has a length of zero, with both iterators pointing to the first element that has a key considered to go after k according to the container's internal comparison object (key_comp).
Two keys are considered equivalent if the container's comparison object returns false reflexively (i.e., no matter the order in which the keys are passed as arguments).
- Key to search for.
Member type key_type is the type of the elements in the container, defined in map as an alias of its first template parameter (Key).
The function returns a pair, whose member pair::first is the lower bound of the range (the same as lower_bound), and pair::second is the upper bound (the same as upper_bound).
If the map object is const-qualified, the function returns a pair of const_iterator. Otherwise, it returns a pair of iterator.
Member types iterator and const_iterator are bidirectional iterator types pointing to elements (of type value_type).
Notice that value_type in map containers is itself also a pair type: pair<const key_type, mapped_type>.
int main ()
ret = mymap.equal_range('b');
std::cout << "lower bound points to: ";
std::cout << ret.first->first << " => " << ret.first->second << '\n';
std::cout << "upper bound points to: ";
std::cout << ret.second->first << " => " << ret.second->second << '\n';
lower bound points to: 'b' => 20
upper bound points to: 'c' => 30
Logarithmic in size.
The container is accessed (neither the const nor the non-const versions modify the container).
No mapped values are accessed: concurrently accessing or modifying elements is safe.
Strong guarantee: if an exception is thrown, there are no changes in the container.
- Count elements with a specific key (public member function)
- Return iterator to lower bound (public member function)
- Return iterator to upper bound (public member function)
- Access element (public member function)
- Get iterator to element (public member function)