【数据结构与算法(java)】数组模拟队列

队列

数组模拟队列

• front = -1; 指向队首前一个位置
• rear = -1; 指向最后一个元素

import java.util.Scanner;

public class ArrayQueueDemo {

    public static void main(String[] args) {
        ArrayQueue arrayQueue = new ArrayQueue(3);
        char key = ' ';
        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 's':
                    arrayQueue.showQueue();
                    break;
                case 'a':
                    System.out.println("输出一个数");
                    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) {
                        //TODO: handle exception
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'h':
                    try {
                        int res = arrayQueue.headQueue();
                        System.out.printf("队列头的的数据是%d\n", res);
                    } catch (Exception e) {
                        //TODO: handle exception
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'e':
                    scanner.close();
                    loop = false;
                    break;
                default:
                    throw new AssertionError();
            }
        }
        System.out.println("程序退出");
    }
}

class ArrayQueue {

    private int maxSize;
    private int front;
    private int rear;
    private int[] arr;

    public ArrayQueue(int arrMaxSize) {
        maxSize = arrMaxSize;
        arr = new int[maxSize];
        front = -1; // 指向队首前一个位置
        rear = -1; // 指向最后一个元素
    }

    public boolean isFull() {
        return rear == maxSize - 1;
    }

    public boolean isEmpty() {
        return rear == front;
    }

    public void addQueue(int n) {
        if (isFull()) {
            System.out.println("队列满");
            return;
        }
        rear++;
        arr[rear] = n;
    }

    public int getQueue() {
        if (isEmpty()) {
            System.out.println("队列空");
            throw new RuntimeException("队列为空，无法取出数据");
        }
        front++;
        return arr[front];
    }

    public void showQueue() {
        if (isEmpty()) {
            System.out.println("队列为空");
            return;
        }
        for (int i = 0; i < arr.length; i++) {
            System.out.printf("arr[%d] = %d  ", i, arr[i]);
        }
        System.out.println();
    }

    public int headQueue() {
        if (isEmpty()) {
            throw new RuntimeException("队列空，无法读取头数据");
        }
        return arr[front + 1];
    }
}