203. 移除链表元素.md

date created	date modified
2022-08-18, 11:29:22	2022-08-18, 11:39:01

Meta

• alias:
• parent :: [[algo-删除链表中的元素]]
• siblings ::
• child ::
• refs: https://leetcode.cn/problems/remove-linked-list-elements/

---

1. 设置 dummy 节点可以避免删除 head 节点带来的额外处理代码
2. 单链表的删除节点操作都需要两个指针：一个 cur 指向当前处理节点，一个 pre 指向前驱结点

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode removeElements(ListNode head, int val) {
        if (head == null) return null;
        ListNode dummy = new ListNode(0, head);
        ListNode cur = head;
        ListNode pre = dummy;
        while (cur != null) {
            if (cur.val == val) {
                pre.next = cur.next;
                // pre 保持不动
            } else {
                pre = cur;
            }
            cur = cur.next;
        }
        return dummy.next;
    }
}