std::equal_range is an STL algorithm to obtain the range equal to a certain value in a container.

In the example below, the range is obtained for the values matching '1':


#include <algorithm>

#include <cassert>

#include <vector>



int main()

{

  std::vector<int> v;

  v.push_back(0);

  v.push_back(1);

  v.push_back(1);

  v.push_back(2);



  typedef std::vector<int>::const_iterator Iterator;

  typedef std::pair<Iterator,Iterator> Pair;

  const Pair p = std::equal_range(v.begin(),v.end(),1);



  //std::equal_range returns iterators pointing to the following positions:

  //0 - 1 - 1 - 2

  //    ^       ^



  assert(*(p.first -1)  == 0);

  assert(*(p.first   )  == 1);

  assert(*(p.second-1)  == 1);

  assert(*(p.second  )  == 2);

}

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(C++) std::equal_range