题解 | 【模板】序列操作

使用ArrayList操作。这个就是对API掌握

import java.util.Scanner;
import java.util.ArrayList;
import java.util.List;
import java.util.Arrays;
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        List<Integer> list = new ArrayList<>();
        int q = in.nextInt();
        for (int i = 0; i < q; i++) {
            int a = in.nextInt();
            switch (a) {
                case 1:
                    list.add(in.nextInt());
                    break;
                case 2:
                    list.remove(list.size()-1);
                    break;
                case 3:
                    System.out.println(list.get(in.nextInt()));
                    break;
                case 4:
                    list.add(in.nextInt()+1,in.nextInt());


                    break;
                case 5:
                    list.sort((o1,o2)->o1-o2);

                    break;
                case 6:
                    list.sort((o1,o2)->o2-o1);

                    break;
                case 7:
                    System.out.println(list.size());

                    break;
                case 8:
                    int len = list.size();
                    for (int j = 0; j < len; j++) {
                        System.out.print(list.get(j));
                        if (j < len - 1) {
                            System.out.print(" ");
                        } else {
                            System.out.println();
                        }
                    }

                    break;

            }
        }
    }
}