Remove Duplicates from Sorted List(链表)

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.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        ListNode p=head;           //这样是跟着动的
        while(p!=null){
            while(p!=null && p.next!=null && p.val==p.next.val){
                p.next=p.next.next;
            }
            p=p.next;
        }
        return head;
    }
}