1、java数据结构和算法---循环队列

直接上代码:

public class CircleArrayQueueLvcai {
private int[] array;
private int maxSize;//循环队列大小
private int front; // 队列头, 这里约定初始值为0,
private int rear ; //队列尾,初始值为0, 这里约定为 队列中最后一位元素的下一个位置(这样约定,意味着该队列的存储容量为 maxSize-1)

//构造
public CircleArrayQueueLvcai(int size){
    maxSize = size;
    array = new int[size];
}
//是否满
public boolean isFull(){
    return (rear+1) % maxSize == front;  //rear+1 = maxSize 此时对maxSize取模式 结果为0
}
//是否空
public boolean isEmpty(){
    return rear == front; //队列尾 = 队列头 = 0 就为空
}

//添加数据
public String add(int num) throws Exception {
    //判断是否满
    if(isFull()){
        throw new Exception("circle Queue is full, you can set num is "+(maxSize-1));
    }

    array[rear] = num;
    //rear++; 这样写不对,, 因为是循环队列,,队列添加满后,,rear自动变为0, 重新开始
    rear = (rear+1) % maxSize;
    return "add success";
}

//出队列
public int push() throws Exception {
    //判断是否为空
    if(isEmpty()){
        throw new Exception("circle array is empty");
    }
    int resultNum = array[front];
    //不能这样写 front++;  循环队列, 要让front 队列头加满后, 自动变为0
    front = (front+1) % maxSize;
    return resultNum;
}

//show circle queue
public void show(){
    //是否为空
    if(isEmpty()){
        System.out.println(" circle queue is empty");
    }
    //从front开始遍历到 有效数据
    for(int i=front; i<front+getAliveNum(); i++){
        System.out.print(array[i]+" ");
    }
    System.out.println();
}
//获取 循环队列有效数据
public int getAliveNum(){
    //获取队列的有效数据: (rear+maxSize-front)%maxSize , 当rear为最后一个元素的下一个位置时,这个公式是成立的
    return (rear+maxSize-front)%maxSize;
}

public static void main(String[] args) throws Exception {
    //创建循环队列, 容量为4
    CircleArrayQueueLvcai circle = new CircleArrayQueueLvcai(5);
    circle.add(1);
    circle.add(2);
    circle.add(3);
    circle.add(4);
    circle.add(4);//这样的循环队列 能存的元素的大小为 size-1
    circle.show();
    //出队列
    //circle.push();
    //circle.push();
    //circle.push();
    //circle.show();
}

}

测试结果:

  public static void main(String[] args) throws Exception {
    //创建循环队列, 容量为4
    CircleArrayQueueLvcai circle = new CircleArrayQueueLvcai(5);
    circle.add(1);
    circle.add(2);
    circle.add(3);
    circle.add(4);
    //circle.add(4);//这样的循环队列 能存的元素的大小为 size-1
    circle.show();
    //出队列
    circle.push();
    //circle.push();
    //circle.push();
    circle.show();
}

结果为:

  public static void main(String[] args) throws Exception {
    //创建循环队列, 容量为4
    CircleArrayQueueLvcai circle = new CircleArrayQueueLvcai(5);
    circle.add(1);
    circle.add(2);
    circle.add(3);
    circle.add(4);
    //circle.add(4);//这样的循环队列 能存的元素的大小为 size-1
    circle.show();
    //出队列
    circle.push();
    circle.push();
    //circle.push();
    circle.show();
}

结果为: