c++ sorting with custom compare function

Question

I have a vector of following type:

std::vector< std::pair< std::pair< int, int >, std::vector > >  neighbors;

I

Answer 1

Lambdas:

std::sort(
    neighbors.begin(),
    neighbors.end(),
    [index](const std::pair< std::pair< int, int >, std::vector > &a,  
            const std::pair< std::pair< int, int >, std::vector > &b)
            { 
                 return ( a.second[index] > b.second[index] );
            }
);  

See What is a lambda expression in C++11? for a detailled introduction.