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

For your second example use the value type:

#

Copy a map to a vector:

typedef map MyMap;
MyMap myMap;
vector< MyMap::value_type > myVec(myMap.begin(), myMap.end());