Doubly-linked list/Traversal

Doubly-linked list/Traversal
You are encouraged to solve this task according to the task description, using any language you may know.

Traverse from the beginning of a doubly-linked list to the end, and from the end to the beginning.

JavaScript

See Doubly-Linked List (element)#JavaScript. The traverse() and print() functions have been inherited from Singly-Linked List (traversal)#JavaScript. <lang javascript>DoublyLinkedList.prototype.getTail = function() {

   var tail;
   this.traverse(function(node){tail = node;});
   return tail;

} DoublyLinkedList.prototype.traverseBackward = function(func) {

   func(this);
   if (this.prev() != null)
       this.prev().traverseBackward(func);

} DoublyLinkedList.prototype.printBackward = function() {

   this.traverseBackward( function(node) {print(node.value())} );

}

var head = createDoublyLinkedListFromArray([10,20,30,40]); head.print(); head.getTail().printBackward();</lang>

outputs:

10
20
30
40
40
30
20
10

Uses the print() function from Rhino or SpiderMonkey.

Ruby

<lang ruby>class DListNode

 def get_tail
   tail = nil
   self.each {|node| tail = node}
   tail
 end

 def each_previous(&b)
   yield self
   self.prev.each_previous(&b) if self.prev
 end

end

head = DListNode.from_array([:a, :b, :c]) head.each {|node| p node.value} head.get_tail.each_previous {|node| p node.value}</lang>