數(shù)組模擬環(huán)形隊(duì)列

充分利用數(shù)組,因此將數(shù)組看做是一個(gè)環(huán)形的。(通過取模的方式來實(shí)現(xiàn)即可)

思路如下:
1.font變量的含義做一個(gè)調(diào)整:font就指向隊(duì)列的第一個(gè)元素,也就是說arr[font]就是隊(duì)列的第一個(gè)元素,front的初始值是0
2.rear變量的含義做一個(gè)調(diào)整:rear指向隊(duì)列的最后一個(gè)元素的后一個(gè)位置,因?yàn)橄Ｍ粘鲆粋€(gè)空間作為約定,rear的初始值=0
3.當(dāng)隊(duì)列滿時(shí),條件是 (rear+1)%maxSize == font 【滿】
4.當(dāng)隊(duì)列為空的條件,rear==front,【空】
5.隊(duì)列中有效的數(shù)據(jù)的個(gè)數(shù): (rear+maxSize-front)%maxSize

代碼實(shí)現(xiàn)

package com.young.queue;

import java.util.Scanner;

public class CircleArrayQueueDemo {

    public static void main(String[] args) {
        System.out.println("測試數(shù)組模擬環(huán)形隊(duì)列的案例~~~");
        //創(chuàng)建一個(gè)環(huán)形隊(duì)列
        CircleArray queue = new CircleArray(4);//說明設(shè)置4,其隊(duì)列的有效數(shù)據(jù)最大是3
        char key = ' ';//接收用戶輸入
        Scanner scanner = new Scanner(System.in);
        boolean loop = true;
        //輸出一個(gè)菜單
        while (loop) {
            System.out.println("s(show):顯示隊(duì)列");
            System.out.println("e(exit):退出程序");
            System.out.println("a(add):添加數(shù)據(jù)到隊(duì)列");
            System.out.println("g(get):從隊(duì)列取出數(shù)據(jù)");
            System.out.println("h(head):查看隊(duì)列頭的數(shù)據(jù)");
            key = scanner.next().charAt(0);//接收一個(gè)字符
            switch (key) {
                case 's':
                    queue.showQueue();
                    break;
                case 'a':
                    System.out.println("輸出一個(gè)數(shù)");
                    int value = scanner.nextInt();
                    queue.addQueue(value);
                    break;
                case 'g'://取出數(shù)據(jù)
                    try {
                        int res = queue.getQueue();
                        System.out.printf("取出的數(shù)據(jù)是%d\n", res);
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'h'://查看隊(duì)列頭的數(shù)據(jù)
                    try {
                        int res = queue.headQueue();
                        System.out.printf("隊(duì)列頭的數(shù)據(jù)是%d\n", res);
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'e'://退出
                    scanner.close();
                    loop = false;
                default:
                    break;
            }
        }

        System.out.println("程序退出~~");
    }

}

class CircleArray {
    private int maxSize;//表示數(shù)組的最大容量
    /**
     * font變量的含義做一個(gè)調(diào)整:font就指向隊(duì)列的第一個(gè)元素,也就是說arr[font]就是隊(duì)列的第一個(gè)元素,front的初始值是0
     */
    private int front;
    /**
     * rear變量的含義做一個(gè)調(diào)整:rear指向隊(duì)列的最后一個(gè)元素的后一個(gè)位置,因?yàn)橄Ｍ粘鲆粋€(gè)空間作為約定,rear的初始值=0
     */
    private int rear;
    private int[] arr;//該數(shù)組用于存放數(shù)據(jù),模擬隊(duì)列

    public CircleArray(int arrMaxSize) {
        maxSize = arrMaxSize;
        arr = new int[maxSize];
    }

    //判斷隊(duì)列是否滿
    public boolean isFull() {
        return (rear + 1) % maxSize == front;
    }

    //判斷隊(duì)列是否為空
    public boolean isEmpty() {
        return rear == front;
    }

    //添加數(shù)據(jù)到隊(duì)列
    public void addQueue(int n) {
        //判斷隊(duì)列是否滿
        if (isFull()) {
            System.out.println("隊(duì)列滿,不能加入數(shù)據(jù)");
            return;
        }
        //直接將數(shù)據(jù)加入
        arr[rear] = n;
        //將rear后移,這里必須考慮取模
        rear = (rear + 1) % maxSize;
    }

    //獲取隊(duì)列的數(shù)據(jù),出隊(duì)列
    public int getQueue() {
        //判斷隊(duì)列是否空
        if (isEmpty()) {
            //通過拋出異常
            throw new RuntimeException("隊(duì)列空,不能取數(shù)據(jù)");
        }
        //這里需要分析出front是指向隊(duì)列的第一個(gè)元素
        //1.先把這個(gè)front對應(yīng)的值保留到一個(gè)臨時(shí)變量
        int value = arr[front];
        //2.將front后移,考慮取模
        front = (front + 1) % maxSize;
        //3.將臨時(shí)保存的變量返回
        return value;
    }

    //顯示隊(duì)列的所有數(shù)據(jù)
    public void showQueue() {
        //遍歷
        if (isEmpty()) {
            System.out.println("隊(duì)列空的,沒有數(shù)據(jù)");
            return;
        }
        //思路:從front開始遍歷,遍歷多少個(gè)元素
        for (int i = front; i < front + size(); i++) {
            System.out.printf("arr[%d]=%d\n", i % maxSize, arr[i % maxSize]);
        }
    }

    //求出當(dāng)前隊(duì)列有效數(shù)據(jù)的個(gè)數(shù)
    public int size() {
        return (rear + maxSize - front) % maxSize;
    }

    //顯示隊(duì)列的頭數(shù)據(jù),注意不是取出數(shù)據(jù)
    public int headQueue() {
        //判斷
        if (isEmpty()) {
            throw new RuntimeException("隊(duì)列空的,沒有數(shù)據(jù)~~");
        }
        return arr[front];
    }

}