Most useful or amazing STL short liners

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:

   vector <...>().swap (v)
   

   (swap with a temporary)

2. Copy a map to a vector:

   map<T1, T2> myMap;
   vector< pair<T1, T2> > myVec(myMap.begin(), myMap.end());
   // or
   myVec.assign(myMap.begin(), myMap.end());
   

3. Custom, non-boost split:

   vector<string> &mysplit(const string &s, char delim, vector<string> &elems) {
       stringstream ss(s);
       string item;
       while(getline(ss, item, delim)) { elems.push_back(item); }
       return elems;
   }