03_队列

 01_概念

---

 02_特点

---

03_分类

---

04_基本运算

---

 05_Java实现

---

 06_Java实现(单向队列)

package DataStructureReview;

public class ArrayQueueDemo {
    public static void main(String[] args) {
        //创建队列对象
        ArrayQueue queue = new ArrayQueue(4);
        //判断空队
        System.out.println("是否空队："+queue.isEmpty());
        //判断满队
        System.out.println("是否满队："+queue.isFull());
        //元素进队
        queue.inQueue(1);
        queue.inQueue(2);
        queue.inQueue(3);
        queue.inQueue(4);
        //queue.inQueue(5);
        System.out.println("front元素为："+queue.getFront());
        queue.printQueue();
        System.out.printf("%d 出队\n",queue.outQueue());
        //"假溢出"现象
        //queue.inQueue(5);



    }
}

class ArrayQueue {
    private int[] arr;
    //front指针：队头元素的指针
    private int front = 0;
    //rear指针：队尾元素的的指针
    private int rear = 0;

    //初始化队列
    public ArrayQueue(int size) {
        this.arr = new int[size];
    }

    //判断空队函数
    public boolean isEmpty() {
        return front == rear;
    }

    //判断满队函数
    public boolean isFull() {
        //单向队列，会出现“假溢出”现象
        return rear == arr.length;
    }

    //入队操作
    public void inQueue(int e) {
        if (isFull()) {
            throw new RuntimeException("此队列已满，无法添加元素");
        }
        arr[rear++] = e;
    }

    //出队操作
    public int outQueue() {
        if (isEmpty()) {
            throw new RuntimeException("此队列为空，无元素可出队");
        }
        return arr[front++];
    }

    //读取队头元素
    public int getFront() {
        if (isEmpty()) {
            throw new RuntimeException("此队列为空，无元素可出队");
        }
        return arr[front];
    }


    //遍历队列元素
    public void printQueue(){
        if(isEmpty()){
            System.out.println("此队列为空");
            return;
        }
        System.out.print("front:<<<  ");
        for (int i = front; i < rear; i++) {
            System.out.print(arr[i]+"  ");
        }
        System.out.println("<<<:rear");
    }

}

---

07_Java实现(环形队列)

package DataStructureReview;

public class CircleArrayQueueDemo {
    public static void main(String[] args) {
        //创建队列对象
        CircleArrayQueue queue = new CircleArrayQueue(5);
        //判断空队
        System.out.println("是否空队：" + queue.isEmpty());
        //判断满队
        System.out.println("是否满队：" + queue.isFull());
        //元素进队
        queue.inQueue(5);
        queue.inQueue(6);
        queue.inQueue(7);
        queue.inQueue(8);
        //queue.inQueue(9);
        System.out.println("front元素为：" + queue.getFront());
        queue.printQueue();
        System.out.printf("%d 出队\n", queue.outQueue());
        //"假溢出"现象
        queue.inQueue(90);
        queue.printQueue();
    }
}

class CircleArrayQueue {
    private int[] arr;
    private int front = 0;
    private int rear = 0;

    //初始化队列
    public CircleArrayQueue(int size) {
        this.arr = new int[size];
    }

    //空队判断
    public boolean isEmpty() {
        return front == rear;
    }

    //满队判断
    public boolean isFull() {
        return (rear + 1) % arr.length == front;
    }

    //入队操作
    public void inQueue(int e) {
        if (isFull()) {
            throw new RuntimeException("此队列已满，无法进行入队操作");
        }
        arr[rear] = e;
        rear = (rear + 1) % arr.length;
    }

    //出队操作
    public int outQueue() {
        if (isEmpty()) {
            throw new RuntimeException("此队列为空，无元素出队");
        }
        int result = arr[front];
        front = (front + 1) % arr.length;
        return result;
    }

    //获取front元素
    public int getFront() {
        if (isEmpty()) {
            throw new RuntimeException("此队列为空，无元素出队");
        }
        int result = arr[front];
        return result;
    }

    //打印队列
    public void printQueue() {
        if (isEmpty()) {
            System.out.println("此队列为空");
            return;
        }
        int front_p = front;
        System.out.print("front:<<<  ");
        while (true) {
            System.out.print(arr[front_p] + "  ");
            front_p = (front_p + 1) % arr.length;
            if (front_p == rear) {
                break;
            }
        }
        System.out.println("<<<:rear");
    }

}