elegant way to remove all elements of a vector that are contained in another vector?

Question

While looking over some code I found loopy and algorithmically slow implementation of std::set_difference :

 for(int i = 0; i < a.size(); i++)
 {
  iter = std         


        

Answer 1

This one does it in O(N+M), assuming both arrays are sorted.

  auto ib = std::begin(two);
  auto iter = std::remove_if (
       std::begin(one), std::end(one),
       [&ib](int x) -> bool {
                       while  (ib != std::end(two) && *ib < x) ++ib;
                       return (ib != std::end(two) && *ib == x);
                     });