public void unionIn(PostingsList other) {
		// Don't do anything if other has no elements
		if (other.size() == 0) {
			return;
		}
		Node<Posting> meCur = this.getHeadNode(), meNext = meCur.next;
		Node<Posting> them = other.getHeadNode().next;
		while (them != null) {
			if (meCur != this.getHeadNode() && 
				them.value.compareTo(meCur.value) == 0) {
				// If them == meCur, advance it
				them = them.next;
			} else if ((meCur == this.getHeadNode() || 
					    meCur.value.compareTo(them.value) < 0) &&
					   (meNext == null ||
					    meNext.value.compareTo(them.value) > 0)) {
				
				// If (them is at the start or them >= meCur) and (them < meNext
				// or there is no meNext), then insert here
				Node<Posting> newNode = new Node<Posting>();
				newNode.value = them.value;
				meCur.next = newNode;
				newNode.next = meNext;
				
				// Advance all pointers forward by one
				them = them.next;
				meCur = newNode;
				meNext = meCur.next;
				
				docIDs.size ++;
			} else {
				// Advance me pointers, them stays the same
				meCur = meNext;
				meNext = meNext.next;
			}	
		}
	}