题解 | #【模板】队列#

import java.util.*;
import java.util.Scanner;
public class Main{
    static Queue<Integer> q = new LinkedList<Integer>();
    static int[] values = null;
    static int size = 0;
    static int head = 0;
    static int lenth = 0;

    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNextLine()){
            //拆分输入
            String input = sc.nextLine();
            String[] inputs = input.split(" ");
            String op = inputs[0];
            //如果数据长度为1
            if(inputs.length > 1){
                //插入操作
                int val = Integer.parseInt(inputs[1]);
                 push(val);
            }else{
                //输出或者出队列操作
                if("pop".equals(op)) pop(); 
                else if("front".equals(op)) front();
                else {
                    lenth = Integer.parseInt(op);
                    values = new int[lenth];
                }
            }
        }
    }
    public static void push(int itme){
        //q.add(itme);
        //考虑重置数组
        if(head + size ==  lenth){
            reset();
        }else{
            values[head + size] = itme;
        }
        size++;
    }
    public static void pop(){
        //if(q.isEmpty()) System.out.println("error");else System.out.println(q.poll());
        if(size == 0){
            System.out.println("error");
        }else{
          System.out.println(values[head]) ;
            head++;
            size--;
        }
    }
   
    public static  void front(){
        if(size == 0){
            System.out.println("error");
        }else{
          System.out.println(values[head]) ;
        }
        //if(q.isEmpty()) System.out.println("error");else System.out.println(q.peek());
    }
    //不需要扩容,需要重置一下
    public static  void reset(){
       //从head开始,遍历size
       for(int i = 0;i < size;i++){
           values[i] = values[head+i];
       }
        head = 0;
    }
}