:type head: ListNode
:rtype: ListNode
"""
node = head;
result = node;
previous = None;
while node != None:
nextNode = node.next;
if nextNode != None:
node.next = nextNode.next;
nextNode.next = node;
if node == head:
result = nextNode;
if previous != None:
previous.next = nextNode;
previous = node;
node = node.next;
return result;
list = [1,2,3,4,5];
controller = ListNodeController();
controller.addAll(list);
listString = controller.toString();
result = Solution().swapPairs(controller.getHead());
resultController = ListNodeController(result);
print '%s = %s' % (listString , resultController.toString());
