数组模拟普通队列与环形队列

​​普通队列​​​​无fuck可speak​​

package com.whb.queue;

import java.util.Scanner;

public class ArrayQueueDemo {

    public static void main(String[] args) {
        //测试一把
        //创建一个队列
        ArrayQueue queue = new ArrayQueue(3);
        char key = ' '; //接收用户输入
        Scanner scanner = new Scanner(System.in);//
        boolean loop = true;
        //输出一个菜单
        while(loop) {
            System.out.println("s(show): 显示队列");
            System.out.println("e(exit): 退出程序");
            System.out.println("a(add): 添加数据到队列");
            System.out.println("g(get): 从队列取出数据");
            System.out.println("h(head): 查看队列头的数据");
            key = scanner.next().charAt(0);//接收一个字符
            switch (key) {
                case 's':
                    queue.showQueue();
                    break;
                case 'a':
                    System.out.println("输出一个数");
                    int value = scanner.nextInt();
                    queue.addQueue(value);
                    break;
                case 'g': //取出数据
                    try {
                        int res = queue.getQueue();
                        System.out.printf("取出的数据是%d\n", res);
                    } catch (Exception e) {
                        // TODO: handle exception
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'h': //查看队列头的数据
                    try {
                        int res = queue.headQueue();
                        System.out.printf("队列头的数据是%d\n", res);
                    } catch (Exception e) {
                        // TODO: handle exception
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'e': //退出
                    scanner.close();
                    loop = false;
                    break;
                default:
                    break;
            }
        }

        System.out.println("程序退出~~");
    }
}

class ArrayQueue{
    private int maxSize;
    private int front;
    private int rear;
    private int[] arr;

    public ArrayQueue(int arrMaxSize){
        maxSize = arrMaxSize;
        arr = new int[maxSize];
        front = -1;
        rear = -1;
    }

    public boolean isFull(){
        return rear == maxSize - 1;
    }

    public boolean isEmpty(){
        return rear == front;
    }

    public void addQueue(int n){
        if(isFull()){
            System.out.println("队列满,不能加入数据");
            return;
        }
        rear++;
        arr[rear] = n;
    }

    public int getQueue(){
        if(isEmpty()){
            throw new RuntimeException("队列为空");
        }else if(front==rear){
            throw new RuntimeException("数据已经取完");
        }
        front++;
        return arr[front];
    }

    public void showQueue(){
        if(isEmpty()){
            System.out.println("空");
            return;
        }
        for (int i = 0; i < arr.length; i++){
            System.out.printf("arr[%d]=%d\n", i, arr[i]);
        }
    }

    public int headQueue(){
        if(isEmpty()){
            throw new RuntimeException("空");
        }
        return arr[front+1];
    }
}

​​环形队列​​
​​​实现环形队列时,front指向队列头部的数据,rear指向最后一个数据的后面,空出来一个用于平衡rear,即指定大小为4时,实际只能存储3个数据​​

判断为空:​​当front和rear指向同一个数据时,表示未存储数据或者数据已经取完​​​ 判断满:​​rear执向末尾数据的下一个位置,当要向队列里边添加数据时rear需要向后移动,如果rear要移动的下一个位置恰好是front头部指向的数据时,表示队列已经满了 即:(rear + 1) % maxSize == front​​ size的判别:​​当rear大于front时,size = rear - front,由于是环形队列,所以rear可能小于front,当rear小于front时,size = maxsize - (rear到front之间空出来的大小) 即：size = maxsize - (front - rear) = maxsize + rear - front​​

Size

空

满
​​​可以看到满之后也会空一个数据位置​​​

package com.whb.queue;
import java.util.Scanner;

public class CircleArrayQueueDemo {

    public static void main(String[] args) {
        //测试一把
        System.out.println("测试数组模拟环形队列的案例~~~");
        
        // 创建一个环形队列
        CircleArray queue = new CircleArray(4); //说明设置4, 其队列的有效数据最大是3
        char key = ' '; // 接收用户输入
        Scanner scanner = new Scanner(System.in);//
        boolean loop = true;
        // 输出一个菜单
        while (loop) {
            System.out.println("s(show): 显示队列");
            System.out.println("e(exit): 退出程序");
            System.out.println("a(add): 添加数据到队列");
            System.out.println("g(get): 从队列取出数据");
            System.out.println("h(head): 查看队列头的数据");
            key = scanner.next().charAt(0);// 接收一个字符
            switch (key) {
            case 's':
                queue.showQueue();
                break;
            case 'a':
                System.out.println("输出一个数");
                int value = scanner.nextInt();
                queue.addQueue(value);
                break;
            case 'g': // 取出数据
                try {
                    int res = queue.getQueue();
                    System.out.printf("取出的数据是%d\n", res);
                } catch (Exception e) {
                    // TODO: handle exception
                    System.out.println(e.getMessage());
                }
                break;
            case 'h': // 查看队列头的数据
                try {
                    int res = queue.headQueue();
                    System.out.printf("队列头的数据是%d\n", res);
                } catch (Exception e) {
                    // TODO: handle exception
                    System.out.println(e.getMessage());
                }
                break;
            case 'e': // 退出
                scanner.close();
                loop = false;
                break;
            default:
                break;
            }
        }
        System.out.println("程序退出~~");
    }
}

class CircleArray{
    private int maxSize;
    private int front;
    private int rear;
    private int[] arr;

    public CircleArray(int arrMaxSizr){
        maxSize = arrMaxSizr;
        arr = new int[maxSize];
    }

    public int size(){
        return (rear + maxSize - front) % maxSize;
    }

    // 判断队列是否满
    public boolean isEmpty(){
        return rear == front;
    }

    public boolean isFull(){
        return (rear+1)%maxSize == front;
    }

    public void addQueue(int n){
        if(isFull()){
            System.out.println("满");
            return;
        }
        arr[rear] = n;
        rear = (rear+1)%maxSize;
    }

    public int getQueue(){
        if(isEmpty()){
            throw new RuntimeException("队列空，不能取数据");
        }

        int value = arr[front];
        front = (front + 1) % maxSize;
        return value;

    }

    public void showQueue(){
        if(isEmpty()){
            System.out.println("empty");
            return;
        }
        for (int i = front; i < front + size();i++){
            System.out.printf("arr[%d]=%d\n", i % maxSize, arr[i % maxSize]);
        }
    }

    // 显示队列的头数据， 注意不是取出数据
    public int headQueue() {
        // 判断
        if (isEmpty()) {
            throw new RuntimeException("队列空的，没有数据~~");
        }
        return arr[front];
    }
}