Leetcode 82: Remove Duplicates from Sorted List II

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

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

 

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode DeleteDuplicates(ListNode head) {
        if (head == null) return null;
        
        ListNode fakeHead = new ListNode(1), priorprior = fakeHead, prior = head, cur = head.next;
        fakeHead.next = head;
        
        while (cur != null)
        {
            if (cur.val != prior.val)
            {
                cur = cur.next;
                prior = prior.next;
                priorprior = priorprior.next;
            }
            else
            {
                while (cur != null && cur.val == prior.val)
                {
                    cur = cur.next;
                    prior = prior.next;
                }
                
                if (cur == null)
                {
                    priorprior.next = null;
                    break;
                }
                
                priorprior.next = cur;
                prior = cur;
                cur = cur.next;
            }
        }
        
        return fakeHead.next;
    }
}