[leetcode]82. Remove Duplicates from Sorted List II有序链表去重(有重删光)

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

Example 1:

Input: 1->2->3->3->4->4->5
Output: 1->2->5

Example 2:

Input: 1->1->1->2->3
Output: 2->3

题意

给定有序链表，凡有重复元素者，删光

思路

指针cur负责边扫旧链表边查重

指针pre负责生成新链表

  

  

代码

class Solution {
      public ListNode deleteDuplicates(ListNode head) {
        if (head == null || head.next == null)  return head;
        ListNode dummy = new ListNode(-1);
        dummy.next = head;
        ListNode pre = dummy;
        ListNode cur = head;

        while (cur!= null) {
            // check duplicates
            while (cur.next != null && cur.val == cur.next.val) {
                cur = cur.next;
            }
            // if cur != pre.next, it means cur moved and duplicates exist
            if (cur != pre.next) {
                pre.next = cur.next;
            } else {
                pre = pre.next;
            }
            cur = cur.next;
        }
        return dummy.next;
    }
}