using pair in set with both values unique code example
Example: find in set of pairs using first value cpp
auto it = std::find_if(st.begin(), st.end(), [](const pair<int,int>& p ){ return p.first == 1; });auto it = std::find_if(st.begin(), st.end(), [](const pair<int,int>& p ){ return p.first == 1; });