Remove Duplicates from Sorted List II

Problem

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

Example

Given 1->2->3->3->4->4->5, return 1->2->5.

Given 1->1->1->2->3, return 2->3.

Code - Java

/**
 * Definition for ListNode
 * public class ListNode {
 *   int val;
 *   ListNode next;
 *   ListNode(int x) {
 *     val = x;
 *     next = null;
 *   }
 * }
 */
public class Solution {
    /**
     * @param ListNode head is the head of the linked list
     * @return: ListNode head of the linked list
     */
    public static ListNode deleteDuplicates(ListNode head) {
        // write your code here
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode p = dummy;
        while (p.next != null) {
            if (p.next.next != null && p.next.val == p.next.next.val) {
                int val = p.next.val;
                while (p.next != null && p.next.val == val) {
                    p.next = p.next.next;
                }
            } else {
                p = p.next;
            }
        }
        return dummy.next;
    }
}