LeetCode 83. Remove Duplicates from Sorted List

Posted 2020-10-18 zeroingToOne

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.

题意：给定一个已经排好序的链表，删除链表中的重复元素

思路；利用pre指向前一个结点，cur指向当前结点，判断两个结点值是否相等。

public ListNode deleteDuplicates(ListNode head) {
　　　　　//要先判断head是否为null，如果在head为null的情况下执行cur = head.next，则相当于对空指针进行操作，会报空指针异常
        if (head == null)
            return head;
        ListNode pre = head;
        ListNode cur = head.next;
        while (cur != null) {
            if (pre.val == cur.val) {
                pre.next = cur.next;
            } 
            else {
                pre = pre.next;
            }
            cur = cur.next;
        }
        return head;
    }