Custom Sorting a vector of tuples

Question

I have a vector of tuples like

vector> v;

I believe that when the default comparison kicks in for tuple types, i

Answer 1

Yes, you can define custom sorting in C++ when you need it. I assume you need it for std::sort, right? Look at the documentation of std::sort, at the second version of the algorithm to be precise, the one which takes the comp argument.

You have to define a less-than functor, something like this:

struct CustomLessThan
{
    bool operator()(tuple const &lhs, tuple const &rhs) const
    {
        return std::get<1>(lhs) < std::get<1>(rhs);
    }
};

And then use it in std::sort:

std::sort(v.begin(), v.end(), CustomLessThan());

In C++11, you can make the code much shorter by using a lambda instead of creating a named struct. The examples given at cppreference.com also show this technique.