题解 | #【模板】循环队列#

/**
少用一个存储位置
当队列为空时条件：rear == front
当队列满时条件为：（rear+1）% maxsize == front
*/
import java.util.Scanner;
class queue{
  private int queueSize = 0;
  private int top = 0;
  private int rear = 0;
  private int[] q;

  void setSize(int queueSize){
    this.queueSize = queueSize;
    this.q = new int[queueSize+1];
  }

  void push(int num){
    if((rear+1)%(queueSize+1) == top){
      System.out.println("full");
    }else{
      q[rear] = num;
      rear = (rear+1)%(queueSize+1);
    }  
  }

  void pop(){
    if(rear == top){
      System.out.println("empty");
    }else{
      System.out.println(q[top]);
      top = (top+1)%(queueSize+1);
    }
  }

  void front(){
    if(rear == top){
      System.out.println("empty");
    }else{
      System.out.println(q[top]);
    }
  }
}
// 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) {
        queue qu = new queue(); 
        Scanner in = new Scanner(System.in);
        String[] str = in.nextLine().split(" ");
        qu.setSize(Integer.parseInt(str[0]));
        int n = Integer.parseInt(str[1]);
        // 注意 hasNext 和 hasNextLine 的区别
        for(int i=0; i<n; i++){
          String[] test = in.nextLine().split(" "); 
          switch(test[0]){
            case "push":
              qu.push(Integer.parseInt(test[1]));
              break;
            case "pop":
              qu.pop();
              break;
            case "front":
              qu.front();
              break;
          }
        }
    }
}