How to create a priority queue of pairs in c++. Which pops the element with min value. The default one pops max

Question

priority_queue < pair < long long int,pair <long long int ,long long int > > > pq;

In this line of code, I want to form a priority_queue on the basis of the first long long int .

The queue pops the min. element.

Answer 1

The std::priority_queue template allows you to specify a type that meets the compare requirement :

typedef mypair pair<long long int, pair<long long int, long long int> >;
std::priority_queue<mypair,
                    std::vector<mypair>,
                    std::greater<mypair> > pq;

If all you need is to reverse the order you can std::greater rather than the default std::less . In cases that require a more complex compare function you can implement your own.