82. Remove Duplicates from Sorted List II

Posted 2020-09-27

 

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.

 

 

需要一个pre记录前一个节点，while循环寻找相同节点的最后一个元素，然后一起删除掉

 

 

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode deleteDuplicates(ListNode head) {
       ListNode temp=new ListNode(0);
        temp.next=head;
        ListNode pre=temp;
        while (head!=null){
            while (head.next!=null&&head.val==head.next.val){
                    head=head.next;
            }
            if (pre.next==head){//no Duplicates
                pre=pre.next;
            }else {// has Duplicates
                pre.next = head.next;
            }
            head=head.next;
        }
        return temp.next;
    }
}