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std::set::equal_range(3) | C++ Standard Libary | std::set::equal_range(3) |
NAME¶
std::set::equal_range - std::set::equal_range
Synopsis¶
std::pair<iterator, iterator> equal_range( const Key&
key ); (1)
std::pair<const_iterator, const_iterator> equal_range( const Key&
(2)
key ) const;
template< class K > (3) (since C++14)
std::pair<iterator, iterator> equal_range( const K& x );
template< class K >
std::pair<const_iterator, const_iterator> equal_range( const K& x
(4) (since C++14)
) const;
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 key and another pointing to the first element greater than key.
Alternatively, the first iterator may be obtained with lower_bound(), and the
second
with upper_bound().
1,2) Compares the keys to key.
3,4) Compares the keys to the value x. This overload participates in overload
resolution only if the qualified-id Compare::is_transparent is valid and
denotes a
type. It allows calling this function without constructing an instance of
Key.
Parameters¶
key - key value to compare the elements to
x - alternative value that can be compared to Key
Return value¶
std::pair containing a pair of iterators defining the wanted
range: the first
pointing to the first element that is not less than key and the second
pointing to
the first element greater than key.
If there are no elements not less than key, past-the-end (see end()) iterator
is
returned as the first element. Similarly if there are no elements greater
than key,
past-the-end iterator is returned as the second element.
Complexity¶
Logarithmic in the size of the container.
Notes¶
Feature-test macro Value Std Feature
Heterogeneous comparison lookup
__cpp_lib_generic_associative_lookup 201304L (C++14) in associative
containers, for
overloads (3,4)
Example¶
// Run this code
#include <iostream>
#include <set>
template<typename I>
void print_equal_range(I first, I lb, I ub, I last)
{
for (I i{first}; i != lb; ++i)
std::cout << *i << ' ';
std::cout << "[ ";
for (I i{lb}; i != ub; ++i)
std::cout << *i << ' ';
std::cout << ") ";
for (I i{ub}; i != last; ++i)
std::cout << *i << ' ';
std::cout << '\n';
}
int main()
{
std::set<int> c{4, 3, 2, 1, 3, 3};
std::cout << "c = ";
print_equal_range(begin(c), begin(c), end(c), end(c));
for (int key{}; key != 6; ++key)
{
std::cout << "key = " << key << "; equal
range = ";
const auto [lb, ub] = c.equal_range(key);
print_equal_range(begin(c), lb, ub, end(c));
}
}
Output:¶
c = [ 1 2 3 4 )
key = 0; equal range = [ ) 1 2 3 4
key = 1; equal range = [ 1 ) 2 3 4
key = 2; equal range = 1 [ 2 ) 3 4
key = 3; equal range = 1 2 [ 3 ) 4
key = 4; equal range = 1 2 3 [ 4 )
key = 5; equal range = 1 2 3 4 [ )
See also¶
find finds element with specific key
(public member function)
contains checks if the container contains element with specific key
(C++20) (public member function)
count returns the number of elements matching specific key
(public member function)
upper_bound returns an iterator to the first element greater than the given
key
(public member function)
lower_bound returns an iterator to the first element not less than the given
key
(public member function)
equal_range returns range of elements matching a specific key
(function template)
2024.06.10 | http://cppreference.com |