队列、环形队列（用数组实现）

 

 

package com.aixuexi.contact;

public class CirArrQunue {
    public static void main(String[] args) {
        /*
         * 2019/7/15 15点58分
         * 2个问题   几个算法公式
         * 
         * 
         *     (rear + 1) % maxSize == front 判断队列是否满
         *     rear = 4      屁股
         *     front = 0     头
         *     maxSize = 5    最大数
         *  (4 + 1) % 5 = 0
         * 
         * 
         *  rear == front
         *     默认 都为0
         * 
         * 
         *     (rear + 1) % maxSize
         *     添加元素 尾指针+1
         *     默认  rear = 0 
         *     maxSize = 5    最大数
         *     rear = (rear + 1) % 5
         * 
         * 
         *     (front + 1) % maxSize
         *     front = (front + 1) % maxSize; //将 front 后移, 考虑取模
         *     默认front = 0     头
         *     front = (0 + 1) % 5         front == 1
         * 
         * 
         *     (rear + maxSize - front) % maxSize    算个数
         *     rear = 3
         *     maxSize = 5
         *     front  = 0 没弹出数据
         *     value = （3 + 5 - 0）%5   valiue == 3
         * 
         * 
         *     显示队列
         *     for(int i = front; i <front + Size(); i++) { //front + Size()     去掉为什么不行
         * 
         * 42行   75 行
         */
        
        CircleArray queue = new CircleArray(5);   //队列有四个元素
        
        System.out.println(queue.isFull());
        System.out.println(queue.isEmpty());
        
        System.out.println(queue.addQueue(7));
        System.out.println(queue.addQueue(8));
        System.out.println(queue.addQueue(1));
        System.out.println(queue.addQueue(9));
        queue.Arrshow();
        
        System.out.println(queue.getQueue());
        queue.Arrshow();
        
        System.out.println(queue.getQueue());
        queue.Arrshow();
        //System.out.println(queue.headQunue());
        
    }
}

class CircleArray{
    
    private int maxSize;
    private int front;
    private int rear;
    private int[] arr;
    //设置队列有多少个元素
    public CircleArray(int arrmaxSize) {
        // 注意： 不要重复定义了 int maxSize 不对 会重新产生变量
        maxSize = arrmaxSize;
        arr = new int[maxSize];
    }
    
    //判断队列是否满
    public boolean isFull() {
        return (rear + 1) % maxSize == front;
    }
    //判断队列是否空
    public boolean isEmpty() {
        return rear == front;
    }
    //添加元素
    public int addQueue(int n) {
        if(isFull()) {
            return -1;
        } 
        arr[rear] = n;
        rear = (rear + 1) % maxSize;//
        return 1;        
    }
    //弹出队列的第一个元素
    public int getQueue() {
        if(isEmpty()) {
            return -1;
        } else {
            int value = arr[front];
            front = (front + 1) % maxSize; //将 front 后移, 考虑取模
            return value;
        }
    }
    //显示队列
    public void Arrshow() {
        for(int i = front; i <front + Size(); i++) { //front + Size()     去掉为什么不行
            System.out.printf("arr[%d]=%d\n", i % maxSize, arr[i % maxSize]);
        }
    }
    //大小 队列
    public int Size() {
        return (rear + maxSize - front) % maxSize;//
    }
    //返回队列头的数值
    public int headQunue() {
        if(isEmpty()) {
            return -1;
        }
        return arr[front];
    }
}