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.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        if (head==null||head.next==null) {
            return head;
        }
        ListNode p = head;
        while (p!=null && p.next!=null) {
            ListNode pNext = p.next;
            //查找pNext
            while (pNext!=null&&p.val==pNext.val) {
                pNext = pNext.next;
            }
            p.next = pNext;
            p = pNext;
        }
        return head;
    }
}