LeetCode | Remove Duplicates from Sorted List

Given a sorted linked list, delete all duplicates such that each element appear only once.

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

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */

 //思想同昨天的从有序数组去重复元素是一样的
public class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        if (head==null || head.next==null) return head;
        
        ListNode pre = head;
        ListNode cur = head.next;       //cur与pre用来在list中找重复
        ListNode non_dup_end = head;    //用来标记无重复list的最后一个节点
        
        while(cur != null){
            if (pre.val != cur.val){    //如果不是重复的话，属正常态，就把non_dup_end向后移一位，然后把cur.val赋过去
                non_dup_end = non_dup_end.next;
                non_dup_end.val = cur.val;
            }
            cur = cur.next;            //如果是重复的话，本次循环什么都不做，直到找到后边第一个不再重复的元素值赋给non_dup_end
            pre = pre.next;
        }
        non_dup_end.next = null;       //不同于数组，循环之后要记得把无重复list后边多余的节点删掉
        return head;
    }
}