[LeetCode]Remove Linked List Elements

Question

Remove all elements from a linked list of integers that have value val.

Example
Given: 1 –> 2 –> 6 –> 3 –> 4 –> 5 –> 6, val = 6
Return: 1 –> 2 –> 3 –> 4 –> 5

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本题难度Easy。

3指针法

复杂度

时间 O(N) 空间 O(1)

思路

很简单，遇到等于val的节点就删除，否则就跳过。

代码

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { val = x; } * } */public class Solution {    public ListNode removeElements(ListNode head, int val) {        //require        if(head==null)return head;        ListNode fake=new ListNode(0);        fake.next=head;        ListNode prev=fake,cur=head;        //invariant        while(cur!=null){            ListNode next=cur.next;            if(cur.val==val){                prev.next=next;                cur.next=null;            }else                            prev=cur;            cur=next;        }        //ensure        return fake.next;    }}