finish DList

This commit is contained in:
Aditya 2022-09-12 18:59:21 +05:30
parent ee19e2974c
commit 150bf2ba9b

View file

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