[Leetcode]Remove Linked List Elements
来源:互联网 发布:算法与数据结构英文 编辑:程序博客网 时间:2024/06/05 11:33
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
Credits:
Special thanks to @mithmatt for adding this problem and creating all test cases.
分析:
1. 对于链表,在删除当前节点时,需要知道当前节点的父节点。
2. 对于非头节点,删除操作很方便,对于头节点需要额外的操作,为了在遍历的过程中,保持删除操作的一致性和避免区分头节点和非头节点,有两种方法来避免这种麻烦:
①可以为链表设置辅助头节点(即在原来链表前插入头节点),这样对具有辅助头节点的链表,在遍历时就不存在区分头节点和非头节点的问题。
The key to solve this problem is using a helper node to track the head of the list.
②从头节点的下一个节点开始遍历查找删除,遍历完成后再处理头节点。
程序一
public class Solution { public ListNode removeElements(ListNode head, int val) { ListNode helpHead = new ListNode(0); helpHead.next = head; ListNode cursor = helpHead; while (cursor.next != null) { if (cursor.next.val == val) { cursor.next = cursor.next.next; } else { cursor = cursor.next; } } return helpHead.next; }}
程序二
public ListNode removeElements(ListNode head, int val) { if (head == null) return null; ListNode pointer = head; while (pointer.next != null) { if (pointer.next.val == val) pointer.next = pointer.next.next; else pointer = pointer.next; } return head.val == val ? head.next : head;}
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