Question

I currently have a std::vector which holds std::vector of double. I’d want to sort it by the second element of the double vectore. ex:
instead of sorting by MyVec[0] or myvec[1] I wat it to sort myVec[0] and myvec[1] based on myvec[0][1] myvec[1][1]. Basically sort by a contained value, not the objects in it.

so if myvec[0][1] is less than myvec[1][1] then myvec[0] and myvec[1] will swap.
Thanks

Answer 1

Just write the comparator:

bool my_comparator(const std::vector<double>& lhs, const std::vector<double>& rhs)
{
  assert(lhs.size() >= 2 && rhs.size() >= 2);
  return lhs[1] < rhs[1];
}
...
std::sort(big_vector.begin(), big_vector.end(), my_comparator);

It is better to write a functor instead of a function, but the concept is the same.