Java数据结构和算法之队列

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​Java数据结构和算法之队列

package Javalearn.dataStructure;
/*
 * @project project
 * @author liyongping
 * @creed: just do it
 * @ date 2021/12/19 10:50
 * @ version 1.0
 */
​
import javax.naming.SizeLimitExceededException;
import java.util.Scanner;
​
class queueTest{
     public static void main(String[] args) {
         queue q=new queue(3);
         char key='a';
         Scanner scanner=new Scanner(System.in);
         boolean loop=true;
         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);
             switch (key){
                 case 'a':
                     System.out.println("请输入一个数");
                     int value=scanner.nextInt();
                     q.addQueue(value);
                     break;
                 case 's':
                     q.showQueue();
                     break;
                 case 'g':
                     try {
                         int res=q.getQueue();
                         System.out.printf("从队列取出数据 %d\n", res);
                     }catch (Exception e){
                         System.out.println(e.getMessage());
                     }
                     break;
                 case 'h':
                     try {
                         int res = q.queueHead();
                         System.out.printf("头部的元素为 %d\n", res);
                     }catch (Exception e){
                         System.out.println(e.getMessage());
                     }
                     break;
                 case 'e':
                     scanner.close();
                     loop=false;
                     break;
                 default:
                     break;
             }
         }
     }
 }
 
class queue {
    int font;//队列的头部位置
    int rear;//对列指针
    int maxSize;//队列的长度
    int [] queue;
    public queue(int size){
         maxSize=size;
         queue=new int[maxSize];
        rear=-1;
        font=-1;
    }
    //队列是否满了
    public boolean isFull(){
        return rear==maxSize-1;
    }
    //队列是否为空
    public boolean isEmpty(){
        return  rear== font;
    }
    //增加数据
    public void addQueue(int addNum) {
        if (this.isFull()) {
            System.out.println("队列已满");
            return;
        }
        rear++;
        queue[rear]=addNum;
    }
    //查
    public int  getQueue(){
        if (isEmpty()){
            throw new RuntimeException("列表中没有数据，运行异常");
        }
         font++;
        return queue[font];
    }
     //打印列表
    public void showQueue(){
        if(isEmpty()){
            System.out.println("数组为空，没有数据");
        }
        for (int i = 0; i <queue.length ; i++) {
            System.out.printf("queue[%d]=%d\n",i,queue[i]);
        }
    }
    //长度
    public int  queueHead(){
        if(isEmpty()){
            System.out.println("数组为空，没有数据");
        }
        return queue[font];
    }
}
​

上述代码运行结果如下：

Java环形队列

package Javalearn.dataStructure;/*
 * @project project
 * @author liyongping
 * @creed: just do it
 * @ date 2021/12/19 16:08
 * @ version 1.0
 */
import javax.naming.SizeLimitExceededException;
import java.util.Scanner;
​
class CircleQueue{
    public static void main(String[] args) {
        CircleArray q=new CircleArray(4);
        char key='a';
        Scanner scanner=new Scanner(System.in);
        boolean loop=true;
        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);
            switch (key){
                case 'a':
                    System.out.println("请输入一个数");
                    int value=scanner.nextInt();
                    q.addQueue(value);
                    break;
                case 's':
                    q.showQueue();
                    break;
                case 'g':
                    try {
                        int res=q.getQueue();
                        System.out.printf("从队列取出数据 %d\n", res);
                    }catch (Exception e){
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'h':
                    try {
                        int res = q.headQueue();
                        System.out.printf("头部的元素为 %d\n", res);
                    }catch (Exception e){
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'e':
                    scanner.close();
                    loop=false;
                    break;
                default:
                    break;
            }
        }
    }
}
class CircleArray {
    private int maxSize;
    private int front;
    private int rear;
    private int[] arr;
​
    public CircleArray(int arrMaxSize) {
        this.maxSize = arrMaxSize;
        this.arr = new int[this.maxSize];
    }
​
    public boolean isFull() {
        return (this.rear + 1) % this.maxSize == this.front;
    }
​
    public boolean isEmpty() {
        return this.rear == this.front;
    }
​
    public void addQueue(int n) {
        if (this.isFull()) {
            System.out.println("队列满，不能加入数据~");
        } else {
            this.arr[this.rear] = n;
            this.rear = (this.rear + 1) % this.maxSize;
        }
    }
​
    public int getQueue() {
        if (this.isEmpty()) {
            throw new RuntimeException("队列空，不能取数据");
        } else {
            int value = this.arr[this.front];
            this.front = (this.front + 1) % this.maxSize;
            return value;
        }
    }
​
    public void showQueue() {
        if (this.isEmpty()) {
            System.out.println("队列空的，没有数据~~");
        } else {
            for(int i = this.front; i < this.front + this.size(); ++i) {
                System.out.printf("arr[%d]=%d\n", i % this.maxSize, this.arr[i % this.maxSize]);
            }
​
        }
    }
​
    public int size() {
        return (this.rear + this.maxSize - this.front) % this.maxSize;
    }
    public int headQueue() {
        if (this.isEmpty()) {
            throw new RuntimeException("队列空的，没有数据~~");
        } else {
            return this.arr[this.front];
        }
    }
}
​

上述代码运行结果如下：