Find the max and min element above a threshold in a container

Question

I have a container that looks like this: std::map<size_t, std::set<char>>

I want to find the absolute max element and the min element above a threshold x based on the size of the std::set .

I can get the max and min using the following line:

auto minMaxElements = std::minmax_element(cbegin(map), cend(map), 
    [](const auto &lhs, const auto &rhs){
        return lhs.second.size() < rhs.second.size();
    });

Is it possible to get the min element above a threshold x using std::minmax_element?

Example: Say I have a std::map of 5 elements. The sizes of the std::set values are as 1, 2, 1, 10, and 5 . And I set the threshold as 1 , then I want the max element to give the iterator containing std::set of size 10 and the min element to give the iterator containing std::set of size 2 .

Answer 1

You can use std::find_if to do that

auto it = std::find_if(map.begin(), map.end(), 
   [x](const auto & l) -> bool { 
      return l.second.size() >= x;    // >= or >, depending upon requirement
   }
);

Then use this iterator in your std::minmax_element

auto minMaxElements = std::minmax_element(it, map.end(), 
    [](const auto & lhs, const auto & rhs) {
        return lhs.second.size() < rhs.second.size();
    }
);