题解 | #【模板】链表#

import java.util.LinkedList;
import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {

    private static LinkedList<Integer> list = new LinkedList<>();
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        final int NUM = in.nextInt();
    
        for (int i = 0; i != NUM; ++i) {
            String op = in.next();

            if (op.equals("insert")) {
                int x = in.nextInt();
                int y = in.nextInt();

                int indexOfX = list.indexOf(x);
                if (indexOfX == -1) {
                    list.addLast(y);
                } else if (indexOfX == 0) {
                    list.addFirst(y);
                } else {
                    list.add(indexOfX, y);
                }    
            }

            if (op.equals("delete")) {
                int x = in.nextInt();

                list.removeFirstOccurrence(x);
            }
        }

        if (list.isEmpty()) {
            System.out.println("NULL");
        } else {

            for (int x : list) {
                System.out.print(x + " ");
            }
        }
    }
}