Doubly Linked Lists

Doubly linked list

Uses two pointers:
struct queue {
struct queue *q_next, *q_prev;
};
Adding and removing elements can be done given only a single element pointer
Example: add elem after head:
    struct queue *next;

    next = head->q_next;
    elem->q_next = next;
    head->q_next = elem;
    elem->q_prev = head;
    next->q_prev = elem;