How will the sorting be done with vector<pair<int,pair<int,int>>>?

Question

In the code sort(A.begin(),A.end()); where A is defined as vector<pair<int,pair<int,int>>> A; .

If I call the sort method, then on which basis will sorting be done?

Answer 1

It will compare using the operator < for the std::pair , specified here .

It compares the elements lexicographically on the first element first, and if they are equal, then on the second element.

Given the complex type here pair<int,pair<int,int>> , it may be a better idea to the give the std::sort algorithm a custom comparator. Make sure that the functor provided fulfils the requirements of the Compare concept, that being strict weak ordering .