multiset::equal_range
Returns a pair of iterators respectively to the first element in a multiset with a key that is greater than a specified key and to the first element in the multiset 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 multiset 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).
Example
// multiset_equal_range.cpp
// compile with: /EHsc
#include <set>
#include <iostream>
int main( )
{
using namespace std;
typedef multiset<int, less<int> > IntSet;
IntSet ms1;
multiset <int> :: const_iterator ms1_RcIter;
ms1.insert( 10 );
ms1.insert( 20 );
ms1.insert( 30 );
pair <IntSet::const_iterator, IntSet::const_iterator> p1, p2;
p1 = ms1.equal_range( 20 );
cout << "The upper bound of the element with "
<< "a key of 20 in the multiset ms1 is: "
<< *( p1.second ) << "." << endl;
cout << "The lower bound of the element with "
<< "a key of 20 in the multiset ms1 is: "
<< *( p1.first ) << "." << endl;
// Compare the upper_bound called directly
ms1_RcIter = ms1.upper_bound( 20 );
cout << "A direct call of upper_bound( 20 ) gives "
<< *ms1_RcIter << "," << endl
<< "matching the 2nd element of the pair"
<< " returned by equal_range( 20 )." << endl;
p2 = ms1.equal_range( 40 );
// If no match is found for the key,
// both elements of the pair return end( )
if ( ( p2.first == ms1.end( ) ) && ( p2.second == ms1.end( ) ) )
cout << "The multiset ms1 doesn't have an element "
<< "with a key less than 40." << endl;
else
cout << "The element of multiset ms1 with a key >= 40 is: "
<< *( p1.first ) << "." << endl;
}
The upper bound of the element with a key of 20 in the multiset ms1 is: 30.
The lower bound of the element with a key of 20 in the multiset ms1 is: 20.
A direct call of upper_bound( 20 ) gives 30,
matching the 2nd element of the pair returned by equal_range( 20 ).
The multiset ms1 doesn't have an element with a key less than 40.
Requirements
Header: <set>
Namespace: std