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finish DList
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@ -11,11 +11,46 @@ class DLink<E> {
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/** Get and set methods for the data members */
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/** Get and set methods for the data members */
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DLink<E> next() { return next; }
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DLink<E> next() { return next; }
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DLink<E> setNext(DLink<E> nextval)
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DLink<E> setNext(DLink<E> nextval)
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{ return next = nextval; }
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{ return next = nextval; }
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DLink<E> prev() { return prev; }
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DLink<E> prev() { return prev; }
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DLink<E> setPrev(DLink<E> prevval)
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DLink<E> setPrev(DLink<E> prevval)
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{ return prev = prevval; }
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{ return prev = prevval; }
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E element() { return element; }
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E element() { return element; }
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E setElement(E it) { return element = it; }
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E setElement(E it) { return element = it; }
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/** Insert "it: at current position */
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public void insert(E it) {
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curr.setNext(new DLink<E>(it, curr, curr.next()));
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curr.next().next().setPrev(curr.next());
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++cnt;
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}
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/** Append "it" to the list */
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public void append(E it) {
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tail.setPrev(new DLink<E>(it, tail.prev(), tail));
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tail.prev().prev().setNext(tail.prev());
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++cnt;
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}
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/** Remove and return current element */
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public E remove() {
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if (curr.next() == tail) return null; // Nothing to remove
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E it = curr.next().element(); // Remember value
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curr.next().next().setPrev(curr);
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curr.setNext(curr.next().next()); // Remove from list
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--cnt; // Decrement the count
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return it;
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}
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/** Move curr one step leftl no change if at front */
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public void prev() {
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if (curr != head) // Can't back up from list head
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curr = curr.prev();
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}
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}
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}
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