(C++17) | ||||
| Sequence | ||||
(C++11) | ||||
(C++26) | ||||
(C++26) | ||||
(C++11) | ||||
| Associative | ||||
| Unordered associative | ||||
(C++11) | ||||
(C++11) | ||||
(C++11) | ||||
(C++11) | ||||
| Adaptors | ||||
(C++23) | ||||
(C++23) | ||||
(C++23) | ||||
(C++23) | ||||
| Views | ||||
(C++20) | ||||
(C++23) | ||||
| Tables | ||||
| Iterator invalidation | ||||
| Member function table | ||||
| Non-member function table |
std::pair<iterator, iterator> equal_range(const Key& key); | (1) | (since C++23) (constexpr since C++26) |
std::pair<const_iterator, const_iterator> equal_range(const Key& key)const; | (2) | (since C++23) (constexpr since C++26) |
template<class K> std::pair<iterator, iterator> equal_range(const K& x); | (3) | (since C++23) (constexpr since C++26) |
template<class K> std::pair<const_iterator, const_iterator> | (4) | (since C++23) (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 isnot less than the given key and another pointing to the first element greater than the given key.
Alternatively, the first iterator may be obtained withlower_bound(), and the second withupper_bound().
Compare istransparent. It allows calling this function without constructing an instance ofKey.Contents |
| key | - | key value to compare the elements to |
| x | - | alternative value that can be compared toKey |
std::pair containing a pair of iterators defining the wanted range:
Logarithmic in the size of the container.
#include <flat_set>#include <functional>#include <print>#include <ranges>#include <string>#include <string_view>#include <tuple> struct Names{std::string forename, surname;friendauto operator<(const Names& lhs,const Names& rhs){returnstd::tie(lhs.surname, lhs.forename)<std::tie(rhs.surname, rhs.forename);}}; struct SurnameCompare{std::string_view surname; friendbool operator<(const Names& lhs,const SurnameCompare& rhs){return lhs.surname< rhs.surname;} friendbool operator<(const SurnameCompare& lhs,const Names& rhs){return lhs.surname< rhs.surname;}}; std::set<Names,std::less<>> characters{{"Homer","Simpson"},{"Marge","Simpson"},{"Lisa","Simpson"},{"Ned","Flanders"},{"Joe","Quimby"}}; void print_unique(const Names& names){auto[begin, end]= characters.equal_range(names);std::print("Found {} characters with name\"{} {}\"\n",std::distance(begin, end), names.forename, names.surname);} void print_by_surname(std::string_view surname){auto[begin, end]= characters.equal_range(SurnameCompare{surname});std::print("Found {} characters with surname\"{}\":\n",std::distance(begin, end), surname);for(const Names& names: std::ranges::subrange(begin, end))std::print(" {} {}\n", names.forename, names.surname);} int main(){ print_unique({"Maude","Flanders"}); print_unique({"Lisa","Simpson"}); print_by_surname("Simpson");}
Output:
Found 0 characters with name "Maude Flanders"Found 1 characters with name "Lisa Simpson"Found 3 characters with surname "Simpson": Homer Simpson Lisa Simpson Marge Simpson
| finds element with specific key (public member function)[edit] | |
| checks if the container contains element with specific key (public member function)[edit] | |
| returns the number of elements matching specific key (public member function)[edit] | |
| returns an iterator to the first elementgreater than the given key (public member function)[edit] | |
| returns an iterator to the first elementnot less than the given key (public member function)[edit] | |
| returns range of elements matching a specific key (function template)[edit] |
