class main {

	public static void main(String[] args) {
		LinkedList ll = new LinkedList();
		ll.append(1);
		ll.append(2);
		ll.append(3);
		ll.append(4);
		ll.append(5);
		ll.append(3);
		ll.retrieve();

		ll.remove(1);
		ll.retrieve();

		ll.removeDups();
		ll.retrieve();
    }

}

class LinkedList {
	Node header;

	static class Node {
		int data;
		Node next = null;
		Node before = null;
	}

	LinkedList() {
		header = new Node();
	}

	void append(int data) {
		Node end = new Node();
		end.data = data;
		Node n = header;

		while(n.next != null) {
			n = n.next;
		}
		end.before = n;
		n.next = end;
	}

	void remove(int data) {
		Node n = header;
		while(n.next != null) {
			if(n.next.data == data) {
				n.next = n.next.next;
				n.next.before = n;
			} else {
				n = n.next;
			}
		}
	}

	void retrieve() {
		Node n = header.next;
		System.out.print("next: ");


		while(n.next != null) {
			System.out.print(n.data + "->");
			n=n.next;
		}
		System.out.println(n.data);
		System.out.print("before: ");


		while(n.before != null) {
			System.out.print(n.data  + "->");
			n=n.before;
		}

		System.out.println();
	}

	void removeDups() {
		Node n = header;
		while(n != null && n.next != null) {
			Node r = n;
			while(r.next != null) {
				if(n.data == r.next.data) {
					r.next = r.next.next;
				} else {
					r = r.next;
				}
			}
			n = n.next;
		}
	}
}