hash_set::equal_range
Returns a pair of iterators respectively to the first element in a hash_set with a key that is greater than a specified key and to the first element in the hash_set with a key that is equal to or greater than the key.
pair <const_iterator, const_iterator> equal_range (
const Key& _Key
) const;
pair <iterator, iterator> equal_range (
const Key& _Key
);
Parameters
- _Key
The argument key to be compared with the sort key of an element from the hash_set being searched.
Return Value
A pair of iterators where the first is the lower_bound of the key and the second is the upper_bound of the key.
To access the first iterator of a pair pr returned by the member function, use pr.first, and to dereference the lower bound iterator, use *(pr.first). To access the second iterator of a pair pr returned by the member function, use pr.second, and to dereference the upper bound iterator, use *(pr.second).
Remarks
In Visual C++ .NET 2003, members of the <hash_map> and <hash_set> header files are no longer in the std namespace, but rather have been moved into the stdext namespace. See The stdext Namespace for more information.
Example
// hash_set_equal_range.cpp
// compile with: /EHsc
#define _DEFINE_DEPRECATED_HASH_CLASSES 0
#include <hash_set>
#include <iostream>
int main( )
{
using namespace std;
using namespace stdext;
typedef hash_set<int> IntHSet;
IntHSet hs1;
hash_set <int> :: const_iterator hs1_RcIter;
hs1.insert( 10 );
hs1.insert( 20 );
hs1.insert( 30 );
pair <IntHSet::const_iterator, IntHSet::const_iterator> p1, p2;
p1 = hs1.equal_range( 20 );
cout << "The upper bound of the element with "
<< "a key of 20 in the hash_set hs1 is: "
<< *(p1.second) << "." << endl;
cout << "The lower bound of the element with "
<< "a key of 20 in the hash_set hs1 is: "
<< *(p1.first) << "." << endl;
// Compare the upper_bound called directly
hs1_RcIter = hs1.upper_bound( 20 );
cout << "A direct call of upper_bound( 20 ) gives "
<< *hs1_RcIter << "," << endl
<< "matching the 2nd element of the pair"
<< " returned by equal_range( 20 )." << endl;
p2 = hs1.equal_range( 40 );
// If no match is found for the key,
// both elements of the pair return end( )
if ( ( p2.first == hs1.end( ) ) && ( p2.second == hs1.end( ) ) )
cout << "The hash_set hs1 doesn't have an element "
<< "with a key less than 40." << endl;
else
cout << "The element of hash_set hs1 with a key >= 40 is: "
<< *(p1.first) << "." << endl;
}
The upper bound of the element with a key of 20 in the hash_set hs1 is: 30.
The lower bound of the element with a key of 20 in the hash_set hs1 is: 20.
A direct call of upper_bound( 20 ) gives 30,
matching the 2nd element of the pair returned by equal_range( 20 ).
The hash_set hs1 doesn't have an element with a key less than 40.
Requirements
Header: <hash_set>
Namespace: stdext