Write a C++ program to find the intersection and/or union of two doubly linked lists using recursion. You are not allowed to use the STL Library.

A set is a collection of distinct entities regarded as a unit, being either individually specified or (more usually) satisfying specified conditions. In set theory the union of two sets A and B, is the is the set of all distinct elements in A and B. The intersection of two sets A and B is the set that contains all elements of A that also belong to B (or equivalently, all elements of B that also belong to A), but no other elements. In mathematics, the notion of bag (or multiset) is a generalization of the notion of set in which members are allowed to appear more than once. For this homework we will work with bags.