Remove Duplicates from Sorted List

/**
 * 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) {
          ListNode p = head;
        ListNode q;

        while( p !=null){
            for( q=p.next; (q!=null) && (q.val==p.val); q=q.next);
            if( q!=null)
                p.next = q;
            else
                p.next = null;
            p = p.next;
        }
        return head;
    }
}