Remove first N elements from a std::vector

Use the .erase() method:

// Remove the first N elements, and shift everything else down by N indices
myvec.erase(myvec.begin(), myvec.begin() + N);

This will require copying all of the elements from indices N+1 through the end. If you have a large vector and will be doing this frequently, then use a std::deque instead, which has a more efficient implementation of removing elements from the front.