题解 | #【模板】队列#

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) {
        Scanner in = new Scanner(System.in);
        int n = Integer.parseInt(in.nextLine());
        MyQueue q = new MyQueue(n);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            String str[] = in.nextLine().split(" ");
            if(str[0].equals("push")){
                q.push(str[1]);
            }
            if(str[0].equals("pop")){
                q.pop();
            }
            if(str[0].equals("front")){
                q.front();
            }
           
        }
    }

}

class MyQueue{
    int front;
    int tail;
    int size;
    String [] nums;
 MyQueue(int size){
        this.front = -1;
        this.tail = -1;
        this.size = size;
        nums = new String[size];
}
    public void pop(){
        if(this.front == this.tail){
            System.out.println("error");
        }else{
            this.front = (this.front + 1)%this.size;
             System.out.println(nums[this.front]);
        }

    }
     public void push(String num){
        if(this.front != (this.tail + 1)%this.size){
        this.tail = (this.tail + 1)%this.size;
            nums[this.tail] = num;
        }

    }

     public void front(){
        if(this.front == this.tail){
            System.out.println("error");
        }else{
             System.out.println(nums[(this.front + 1)%this.size]);
        }

    }

}