如何使用STL的copy（）从现有矢量创建新矢量？

Question

Say I have a std::vector called vec with 10 elements and I want to create a new std::vector containing all elements between (and including) the 2nd and 5th elements of vec. I can see how I might write a for loop to do this, but it looks like STL's copy() can do this more concisely. But I'm not really getting iterators: I've seen how you can use start() and end() to iterate over a vector from its first to last element, but what about the situation above, where I want something slightly different? Thanks.

Answer 1

You don't need std::copy to create a new vector with a subset of the first one. You can achieve this with the vector 's constructor and its iterators ( doc here ):

std::vector<myType> vec = ...;
std::vector<myType> other(vec.begin() + 1, vec.begin() + 5);

You have to be sure though, that you don't exceed the vector 's limits, or you will get undefined behavior.

Answer 2

Constantinus is right with his answer - you don't need copy.

But in case of a different situation, where you want to append elements you can use this:

std::vector< type > vec = ... ;
std::vector< type > othervec = ...;
std::copy( vec.begin(), vec.end(), std::back_inserter(othervec) );