leetcode83~Remove Duplicates from Sorted List

Given a sorted linked list, delete all duplicates such that each element appear only once.
For example,
Given 1->1->2, return 1->2.
Given 1->1->2->3->3, return 1->2->3.

public class RemoveDuplicatesfromSortedList {    //迭代实现    public ListNode deleteDuplicates(ListNode head) {        if(head==null) return null;        ListNode node = head;        while(node.next!=null) {            if(node.val==node.next.val) {                node.next = node.next.next;            } else {                node = node.next;            }        }        return head;    }    //递归实现    public ListNode deleteDuplicates2(ListNode head) {        if(head==null || head.next==null) return head;        head.next = deleteDuplicates2(head.next);        if(head.val==head.next.val) {            return head.next;        } else {            return head;        }    }}