class DNode {
// Node for building a Doubly-linked list
    String contents;
    DNode next;
    DNode prev;

    DNode (String k) {  // Constructor: builds a node which can be searched forwards and backwards
        next= null; prev= null;
        contents= k;
    }

    DNode (String k, DNode prev, DNode next){ // Constructor: builds a node with given references
        this.prev = prev;
        this.next = next;
        this.contents = k;
    }

    void insertAfter(DNode curr, DNode newNode) { //TODO
        // Pre: curr and newNode are addresses for DNodes
        // Post: newNode is inserted between curr and its next neighbour, i.e.
        // let N be newNode's next neighbour, then: curr.next points to newNode, newNode.next points to N
        // N.prev points to newNode and newNode.prev points to curr.
        // If curr has no next neighbour, then newNode is inserted as the last node after curr.
    }