C++ multiset equal_range() function

C++ multiset equal_range() Function with Examples on tutorial for beginners and professionals with examples on multiset, begin(), end(), multiset constructor, ~multiset destructor, operator=, rbegin(), rend() etc.

<< Back to CPP

next → ← prev

C++ Multiset equal_range()

C++ Multiset equal_range() function is used to return the boundary of the range containing all elements in the container that are equal to val.

If val does not match any value in the container, the return value range will be length 0 and both iterators will point to the nearest value greater than val. Otherwise, if val is greater than all elements in the container, it points to end.

Syntax

pair<const_iterator,const_iterator> equal_range (const value_type& val) const;
pair<iterator,iterator>                    equal_range (const value_type& val);

The range is defined by two iterators, one points to the first element that is not less than value val and another points to the first element greater than value val.

Parameter

val: value to be searched in the multiset container.

Return value

This function returns pair. Where pair:: first is at the lower boundary of the range with the same value that lower_bound (val) would return, pair :: second is the same value as the upper_bound (val) would return, upper bound of the range it corresponds to.

Complexity

Logarithmic in size.

Iterator validity

No changes.

Data Races

The container is accessed (neither the const not non-const versions modify the container).

Concurrently accessing the elements of a multiset is safe.

Exception Safety

If an exception is thrown, there are no changes in the container.

Example 1

Let's see the simple example:

#include <iostream>
#include <set>

using namespace std;

int main(void) {
   multiset<char> m = {'a','b','c','a'};

   auto ret = m.equal_range('b');

   cout << "Lower bound of b is: " << *ret.first<< endl;

   cout << "Upper bound of b is: " << *ret.second<< endl;

   return 0;
}

Output:

Lower bound of b is: b
Upper bound of b is: c

In the above example, lower bound of b is b and upper bound of b is c.

Example 2

Let's see a simple example:

#include <iostream>
#include <set>

using namespace std;
 
int main()
{
     // initialize container
    multiset<int> mp;
 
    // insert elements in random order
    mp.insert( 4 );
    mp.insert( 1 );
    mp.insert( 4 );
 
    pair<multiset<int>::const_iterator,multiset<int>::const_iterator> ret;
 
    ret = mp.equal_range(10);
    cout << "The lower bound is: " << *ret.first;
    cout << "\nThe upper bound is: " << *ret.second;
 
    return 0;
}

Output:

The lower bound is 3
The upper bound is 3

In the above example, equal_range() function returns to the end() i.e. 3 because it tries to find 10 which is not present in the multiset mp therefore, it returns to the end.

Example 3

Let's see a simple example:

#include <set>  
#include <iostream>  
  
int main( )  
{  
   using namespace std;  
   typedef multiset<int, less< int > > IntMultiset;  
   IntMultiset s1;  
   multiset <int, less< int > > :: const_iterator s1_RcIter;  
  
   s1.insert( 10 );  
   s1.insert( 20 );  
   s1.insert( 30 );  
  
   pair <IntMultiset::const_iterator, IntMultiset::const_iterator> p1, p2;  
   p1 = s1.equal_range( 20 );  
  
   cout << "The upper bound of the element with "  
        << "a key of 20 in the multiset s1 is: "  
        << *(p1.second) << "." << endl;  
  
   cout << "The lower bound of the element with "  
        << "a key of 20 in the multiset s1 is: "  
        << *(p1.first) << "." << endl;  
  
   // Compare the upper_bound called directly   
   s1_RcIter = s1.upper_bound( 20 );  
   cout << "A direct call of upper_bound( 20 ) gives "  
        << *s1_RcIter << "," << endl  
        << "matching the 2nd element of the pair"  
        << " returned by equal_range( 20 )." << endl;  
  
   p2 = s1.equal_range( 40 );  
  
   // If no match is found for the key,  
   // both elements of the pair return end( )  
   if ( ( p2.first == s1.end( ) ) && ( p2.second == s1.end( ) ) )  
      cout << "The multiset s1 doesn't have an element "  
           << "with a key less than 40." << endl;  
   else  
      cout << "The element of multiset s1 with a key >= 40 is: "  
           << *(p1.first) << "." << endl; 
           
           return 0;
}

Output:

The upper bound of the element with a key of 20 in the multiset s1 is: 30.
The lower bound of the element with a key of 20 in the multiset s1 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 s1 doesn't have an element with a key less than 40.

Example 4

Let?s see a simple example:

#include <iostream>
#include <set>

using namespace std;

int main ()
{
  std::multiset<int> mymultiset;

  for (int i=1; i<=5; i++) mymultiset.insert(i*10);   // mymultiset: 10 20 30 40 50

  pair<std::multiset<int>::const_iterator,multiset<int>::const_iterator> ret;
  ret = mymultiset.equal_range(30);

  cout << "the lower bound points to: " << *ret.first << '\n';
  cout << "the upper bound points to: " << *ret.second << '\n';

  return 0;
}

Output:

the lower bound points to: 30
the upper bound points to: 40

Next TopicC++ multiset

← prev next →

.Net

.NET Array Dictionary List String 2D Async DataTable Dates DateTime Enum File For Foreach Format IEnumerable If IndexOf Lambda LINQ Parse Path Process Property Regex Replace Sort Split Static StringBuilder Substring Switch Tuple

Java

Core Array ArrayList HashMap String 2D Cast Character Console Deque Duplicates File For Format HashSet If IndexOf Lambda Math ParseInt Process Random Regex Replace Sort Split StringBuilder Substring Switch Vector While

TheDeveloperBlog.com

C++ multiset equal_range() function

C++ Multiset equal_range()

Syntax

Parameter

Return value

Complexity

Iterator validity

Data Races

Exception Safety

Example 1

Example 2

Example 3

Example 4

Related Links:

.Net

Java

Related Links