[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

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;
}
}