public member function
<unordered_map>

std::unordered_multimap::equal_range

pair<iterator,iterator>
   equal_range ( const key_type& k );
pair<const_iterator,const_iterator>
   equal_range ( const key_type& k ) const;
Get range of elements with specific key
Returns the bounds of a range that includes all the elements in the container with a key that compares equal to k.

If k does not match any key in the container, the range returned has end as both its lower and upper range bounds.

Parameters

k
Key value to be compared.
Member type key_type is the type of the keys for the elements in the container, defined in unordered_multimap as an alias of its first template parameter (Key).

Return value

The function returns a pair, where its member pair::first is an iterator to the lower bound of the range, and pair::second is an iterator to its upper bound. The elements in the range are those between these two iterators, including pair::first, but not pair::second.

Member types iterator and const_iterator are forward iterator types.

Example

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// unordered_multimap::equal_range
#include <iostream>
#include <string>
#include <unordered_map>
#include <algorithm>

typedef std::unordered_multimap<std::string,std::string> stringmap;

int main ()
{
  stringmap myumm = {
     {"orange","FL"},
     {"strawberry","LA"},
     {"strawberry","OK"},
     {"pumpkin","NH"}
  };

  std::cout << "Entries with strawberry:";
  auto range = myumm.equal_range("strawberry");
  for_each (
    range.first,
    range.second,
    [](stringmap::value_type& x){std::cout << " " << x.second;}
  );

  return 0;
}


Output:
Entries with strawberry: LA OK

Complexity

Average case: constant.
Worst case: linear in container size.

Iterator validity

No changes.

See also

  • 997351548 2018-02-20
  • 903691547 2018-02-20
  • 9127171546 2018-02-20
  • 2234751545 2018-02-20
  • 1685381544 2018-02-20
  • 911091543 2018-02-20
  • 9281021542 2018-02-20
  • 632231541 2018-02-20
  • 9751491540 2018-02-20
  • 8333621539 2018-02-20
  • 995001538 2018-02-20
  • 6477441537 2018-02-20
  • 511981536 2018-02-19
  • 2072881535 2018-02-19
  • 6024461534 2018-02-19
  • 7594061533 2018-02-19
  • 9311341532 2018-02-19
  • 4928331531 2018-02-19
  • 38561530 2018-02-19
  • 7776611529 2018-02-19