hash_map::equal_range
Note
This API is obsolete. The alternative is unordered_map Class.
Returns a pair of iterators respectively to the first element in a hash_map with a key that is greater than a specified key and to the first element in the hash_map 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 value to be compared with the sort key of an element from the hash_map being searched.
Return Value
A pair of iterators such that 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_map_equal_range.cpp
// compile with: /EHsc
#include <hash_map>
#include <iostream>
int main( )
{
using namespace std;
using namespace stdext;
typedef hash_map <int, int> IntMap;
IntMap hm1;
hash_map <int, int> :: const_iterator hm1_RcIter;
typedef pair <int, int> Int_Pair;
hm1.insert ( Int_Pair ( 1, 10 ) );
hm1.insert ( Int_Pair ( 2, 20 ) );
hm1.insert ( Int_Pair ( 3, 30 ) );
pair <IntMap::const_iterator, IntMap::const_iterator> p1, p2;
p1 = hm1.equal_range( 2 );
cout << "The lower bound of the element with "
<< "a key of 2 in the hash_map hm1 is: "
<< p1.first -> second << "." << endl;
cout << "The upper bound of the element with "
<< "a key of 2 in the hash_map hm1 is: "
<< p1.second -> second << "." << endl;
// Compare the upper_bound called directly
hm1_RcIter = hm1.upper_bound( 2 );
cout << "A direct call of upper_bound( 2 ) gives "
<< hm1_RcIter -> second << "," << endl
<< " matching the 2nd element of the pair"
<< " returned by equal_range( 2 )." << endl;
p2 = hm1.equal_range( 4 );
// If no match is found for the key,
// both elements of the pair return end( )
if ( ( p2.first == hm1.end( ) ) && ( p2.second == hm1.end( ) ) )
cout << "The hash_map hm1 doesn't have an element "
<< "with a key less than 40." << endl;
else
cout << "The element of hash_map hm1 with a key >= 40 is: "
<< p1.first -> first << "." << endl;
}
The lower bound of the element with a key of 2 in the hash_map hm1 is: 20. The upper bound of the element with a key of 2 in the hash_map hm1 is: 30. A direct call of upper_bound( 2 ) gives 30, matching the 2nd element of the pair returned by equal_range( 2 ). The hash_map hm1 doesn't have an element with a key less than 40.
Requirements
Header: <hash_map>
Namespace: stdext