c++ - Finding the upper bound of vector of pairs based on second value of pair -

i have vector of pair "v" sorted according second value of pair. want find out upper bound of vector "v" according second value of pair -- while finding upper bound want ignore first vector (std::vector<int>) of pair of vectors.

int main () {   std::vector<std::pair<std::vector<int>, int> > v;           //10 10 10 20 20 20 30 30    std::vector<int> a;   a.push_back(1);   v.push_back(make_pair(a,10));   a.push_back(2);   v.push_back(make_pair(a,10));   a.push_back(3);   v.push_back(make_pair(a,10));   a.push_back(4);   v.push_back(make_pair(a,20));   a.push_back(5);   v.push_back(make_pair(a,20));   a.push_back(6);   v.push_back(make_pair(a,20));   a.push_back(7);   v.push_back(make_pair(a,30));   a.push_back(8);   v.push_back(make_pair(a,30));    std::vector<std::pair<std::vector<int>, int> >::iterator low,up;   std::vector<int> b;   up= std::upper_bound (v.begin(), v.end(), make_pair(b,25));     std::cout << "upper_bound @ position " << (up - v.begin())<<" val="<<v[(up-v.begin())].second<< '\n';    return 0; } 

i want upper_bound position returned 6 , value returned 30. using above code incorrectly getting position 0 , value 10. can please suggest how can upper bound based on second value of pair , ignore first value of pair

you need offer compare function upper_bound

---

template<typename t> bool compare(const t &a,const t &b){     return a.second<b.second; } 

and change:

up= std::upper_bound (v.begin(), v.end(), make_pair(b,25)); 

to:

up= std::upper_bound (v.begin(), v.end(), make_pair(b,25),compare<pair<vector<int>,int>>);