What is the time complexity of std::sort() in the C++ standard library?

Question

What is the complexity of std::sort() in the C++ Standard Library? Which sort is applied? Is there any rule of applying any particular sorting algorithm there?<

Answer 1

Before C++11:

std::sort must have average case linearithmic (n log n) time complexity. Any algorithm may be used so long as that time complexity requirement is met. There is no worst case time complexity requirement.

If you want a guaranteed worst case time complexity function, use std::stable_sort, which has quasilinear worst case time complexity (n log^2 n).