题解 | #【模板】循环队列#

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(
            new InputStreamReader(System.in)
        );
        String[] array = br.readLine().split(" ");
        int capacity = Integer.parseInt(array[0]);
        int len = Integer.parseInt(array[1]);
        Deque<String> dq = new ArrayDeque<>(capacity);
        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < len; i++) {
            String str = br.readLine();
            if (str.equals("pop")) {
                if (dq.isEmpty()) {
                    sb.append("empty").append("\n");
                    continue;
                }
                sb.append(dq.remove()).append("\n");
            } else if (str.equals("front")) {
                if (dq.isEmpty()) {
                    sb.append("empty").append("\n");
                    continue;
                }
                sb.append(dq.element()).append("\n");
            } else {
                if (dq.size() == capacity) {
                    sb.append("full").append("\n");
                    continue;
                }
                dq.add(str.substring(5));
            }
        }
        System.out.println(sb);
    }
}