Most useful or amazing STL short liners

Question

I\'m looking for practical and educational samples of C++ / STL code fitting in few lines. My actual favorites are:

1. Empty a vector freeing its reserved memory:<

Answer 1

What I like most is to use bind1st/bind2nd/mem_fun in sort of delegates.

// will call a->func(v[i])
for_each(v.begin(), v.end(), bind1st(mem_fun(&A::func), &a));

// will call w[i]->func(72)
for_each(w.begin(), w.end(), bind2nd(mem_fun(&A::func), 72));

Using boost's bind and function are much better, but it is impressive which can be done with just STL.