Search variable/item/attribute using STL in c++?

Question

There is any way to search an item or attribute or variable in C++ using STL .
We can use any container of STL providing Searching time as less as possible . Container contains pair<int,int> . i would like to search a pair p(a,x) which should return all pairs X whose p.first == Xi.first and p.second != Xi.second for all i .
e.g.
Let container is unordered_set .

  unordered_set< pair<int , int > > myset =
  {{1,2},{1,5},{1,6},{2,4},{3,5},{4,6},{6,7},{6,8}};
  if i search for p(1,5) then it should return pair(1,2),(1,6)
  if i search for p(2,4) or (3,5),(6,7) then it should return NULL i.e. nothing
  if i search for p(6,7) then it should return pair(6,8)

Answer 1

Something along the lines of

std::vector<std::pair<int, int>> 
  find_nonmatching_values(const std::unordered_multimap<int, int> & thing,
                          int key, int value) {
    std::vector<std::pair<int, int>> ret;
    auto range = thing.equal_range(key);
    std::copy_if(range.first, range.second, std::back_inserter(ret),
                 [value](const std::pair<const int, int> &p) 
                 { return p.second != value; });
    return ret;
}

Demo. Templatizing this code is left as an exercise for the reader.