vector::assign

"assign" is a method in STL for the vector class. When ever you need to erase the contents of the vector and replace it with totally new contents use the assign member function .You should use the operator= then all elements of the right hand side container would be copied to the container on the left hand side.

e.g

v1.assign(v2.begin() + v2.size()/2 , v2.end())