基本介绍
数组模拟队列
代码实现
package com.wustyq.queue;
import java.util.Scanner;
/**
* ClassName: ArrayQueueDemo <br/>
* Description: <br/>
* date: 2021/9/10 21:53<br/>
*
* @author yiqi<br />
* @since JDK 1.8
*/
public class ArrayQueueDemo {
public static void main(String[] args) {
ArrayQueue arrayQueue = 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);
switch (key) {
case 's':
arrayQueue.showQueue();
break;
case 'a':
System.out.println("请输入一个数");
int value = scanner.nextInt();
arrayQueue.addQueue(value);
break;
case 'g':
try {
int res = arrayQueue.getQueue();
System.out.printf("取出的数据是%d\n", res);
} catch (Exception e) {
System.out.println(e.getMessage());
}
break;
case 'h':
try {
int res = arrayQueue.headQueue();
System.out.printf("队列头的数据是%d\n", res);
} catch (Exception e) {
System.out.println(e.getMessage());
}
break;
case 'e':
scanner.close();
loop = false;
break;
default:
break;
}
}
System.out.println("程序退出");
}
}
//使用数组模拟队列 - 编写一个ArrayQueue类
class ArrayQueue {
private int maxSize; //表示数组的最大容量
private int front; //队列头
private int rear; //队列尾
private int[] arr; //该数据用于存放数据，模拟队列
//创建队列的构造器
public ArrayQueue(int maxSize) {
this.maxSize = maxSize;
arr = new int[this.maxSize];
front = -1; //指向队列头部，分析出front是指向队列头的前一个位置
rear = -1; //指向队列尾，指向队列尾的数据（即就是队列最后一个数据）
}
//判断队列是否满
public boolean isFull() {
return rear == maxSize - 1;
}
//判断队列是否为空
public boolean isEmpty() {
return rear == front;
}
//添加数据到队列
public void addQueue(int n) {
//判断队列是否满
if (isFull()) {
System.out.println("队列满，不能加入数据");
return;
}
rear++;
arr[rear] = n;
}
//获取队列的数据
public int getQueue() {
//判断队列是否为空
if (isEmpty()) {
//通过抛出异常
throw new RuntimeException("队列空不能取数据");
}
front++;
return arr[front];
}
//显示队列的所有数据
public void showQueue() {
//遍历
if (isEmpty()) {
System.out.println("队列空的，没有数据");
return;
}
for (int i = 0; i < arr.length; i++) {
System.out.printf("arr[%d]=%d\n", i, arr[i]);
}
}
//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 + 1];
}
}
问题分析并优化
- 目前数组使用一次就不能用，没有达到复用的效果
- 将这个数组使用算法，改进成一个环形的队列 %
优化思路
代码实现
package com.wustyq.queue;
import java.util.Scanner;
/**
* ClassName: CircleArrayQueue <br/>
* Description: <br/>
* date: 2021/9/12 21:01<br/>
*
* @author yiqi<br />
* @since JDK 1.8
*/
public class CircleArrayQueue {
public static void main(String[] args) {
CircleArray arrayQueue = new CircleArray(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);
switch (key) {
case 's':
arrayQueue.showQueue();
break;
case 'a':
System.out.println("请输入一个数");
int value = scanner.nextInt();
arrayQueue.addQueue(value);
break;
case 'g':
try {
int res = arrayQueue.getQueue();
System.out.printf("取出的数据是%d\n", res);
} catch (Exception e) {
System.out.println(e.getMessage());
}
break;
case 'h':
try {
int res = arrayQueue.headQueue();
System.out.printf("队列头的数据是%d\n", res);
} catch (Exception e) {
System.out.println(e.getMessage());
}
break;
case 'e':
scanner.close();
loop = false;
break;
default:
break;
}
}
System.out.println("程序退出");
}
}
class CircleArray {
private int maxSize; //表示数组的最大容量
private int front; //队列头
private int rear; //队列尾
private int[] arr; //该数据用于存放数据，模拟队列
public CircleArray(int maxSize) {
this.maxSize = maxSize;
arr = new int[maxSize];
front = 0;
rear = 0;
}
//判断是否为空
private boolean isFull() {
return (rear + 1) % maxSize == front;
}
//判断是否为空
private boolean isEmpty() {
return rear == front;
}
//添加数据
public void addQueue(int n) {
if (isFull()) {
System.out.println("队列已满");
return;
}
arr[rear] = n;
rear = (rear + 1) % maxSize;
}
//取出数据
public int getQueue() {
if (isEmpty()) {
//通过抛出异常
throw new RuntimeException("队列空不能取数据");
}
int ret = arr[front];
front = (front + 1) % maxSize;
return ret;
}
//显示队列的所有数据
public void showQueue() {
if (isEmpty()) {
//通过抛出异常
System.out.println("队列空不能取数据");
return;
}
//思路：从front开始遍历 遍历多少个元素
for (int i = front; i < front + size(); i++) {
System.out.printf("arr[%d]=%d\n", i % maxSize, arr[i % maxSize]);
}
}
//求出当前队列有效数据的个数
private int size() {
return (rear + maxSize - front) % maxSize;
}
public int headQueue() {
//判断
if (isEmpty()) {
throw new RuntimeException("队列空的，没有数据");
}
return arr[front];
}
}
