隊(duì)列

該文是觀看尚硅谷韓老師視頻學(xué)習(xí)自己總結(jié)學(xué)習(xí)得,有的是來(lái)源于網(wǎng)絡(luò)收集

隊(duì)列引入

進(jìn)的一端稱為隊(duì)尾（rear），出的一端稱為隊(duì)頭（front）。隊(duì)列可以用順序存儲(chǔ)，也可以用鏈?zhǔn)酱鎯?chǔ)。

隊(duì)列介紹

隊(duì)列是一個(gè)**有序列表**，可以用數(shù)組或是鏈表來(lái)實(shí)現(xiàn)。

遵循先入先出的原則。即：先存入隊(duì)列的數(shù)據(jù)，要先取出。后存入的要后取出

示意圖：(使用數(shù)組模擬隊(duì)列示意圖)

數(shù)組模擬隊(duì)列

隊(duì)列本身是有序列表，若使用數(shù)組的結(jié)構(gòu)來(lái)存儲(chǔ)隊(duì)列的數(shù)據(jù)，則隊(duì)列數(shù)組的 如上圖,其中 maxSize 是該隊(duì)列的最大容量。

思路分析
添加數(shù)據(jù)的時(shí)候?qū)⑽仓羔樛笠?#xff1a;rear+1 , 當(dāng) 取出的數(shù)據(jù)front+1,若front == rear 【所明隊(duì)列數(shù)據(jù)為空,并非數(shù)組數(shù)據(jù)空,】
若尾指針 rear 小于隊(duì)列的最大下標(biāo) maxSize-1，則將數(shù)據(jù)存入 rear 所指的數(shù)組元素中，否則無(wú)法存入數(shù)據(jù)。
rear = = maxSize - 1[隊(duì)列滿]

代碼模擬數(shù)組實(shí)現(xiàn)隊(duì)列

package com.fs.demo_2020_07_11_queueArray;import java.util.Scanner;/*** 隊(duì)列* 隊(duì)列是一個(gè)有序列表,可以用數(shù)組或者鏈表來(lái)實(shí)現(xiàn)* 遵循先入先出的原則,先存入的數(shù)據(jù)先取出來(lái),后存入的后取出來(lái)** 數(shù)組模擬隊(duì)列*/ public class QueueArray {public static void main(String[] args) {//測(cè)試一把//創(chuàng)建一個(gè)隊(duì)列SimulationQueueArray queue = new SimulationQueueArray(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());e.printStackTrace();}break;case 'e': //退出scanner.close();loop = false;break;default:break;}}System.out.println("程序退出~~");} }//創(chuàng)建一個(gè)類(lèi)來(lái)模擬隊(duì)列 class SimulationQueueArray {private int maxSize;//表示數(shù)字的最大容納量private int front;//模擬指針,默認(rèn)指向數(shù)組有效數(shù)據(jù)索引的前一個(gè)位置private int rear;//模擬指針指向尾部數(shù)據(jù),默認(rèn)初始化指向和front一個(gè)位置,因?yàn)闆](méi)有數(shù)據(jù)private int[] arr;/*** 創(chuàng)建隊(duì)列數(shù)組的構(gòu)造器** @param arrMaxSize 初始化這個(gè)隊(duì)列數(shù)組的容量*/public SimulationQueueArray(int arrMaxSize) {maxSize = arrMaxSize;arr = new int[maxSize];//初始化數(shù)組的容量front = -1;rear = -1;}//判斷隊(duì)列數(shù)組是否滿了public boolean isFull() {//假設(shè)數(shù)組最大索引為2,那么容量就為3,當(dāng)添加3個(gè)數(shù)據(jù)后,rear就加了3次,就是-1+3=2//所以-1+3 = 2 = 3 -1 = 2,所以就滿了return rear == maxSize - 1;}//判斷隊(duì)列是否為空public boolean isEmpty() {//為空有兩中情況,//1.就是數(shù)組中的元素取完了,我還是假設(shè)容量為3,要么一條數(shù)據(jù)都沒(méi)有添加,front和rear都為-1,表示容量為空//2.數(shù)組中的元素添加3個(gè),那么front為2,然后我們又取了3個(gè)元素,那么front也為2,那么rear=front,說(shuō)明數(shù)組中為空return rear == front;}//添加數(shù)據(jù)到隊(duì)列public void addQueue(int data) {//添加前先判斷隊(duì)列是否滿了if (isFull()) {System.out.println("隊(duì)列滿,不能加入數(shù)據(jù)~~~");return;}rear++;//讓指針向后移一下//在rear索引下添加這個(gè)數(shù)據(jù),假設(shè)第一次添加,就是0索引添加data數(shù)據(jù)arr[rear] = data;}//獲取隊(duì)列的數(shù)據(jù),出隊(duì)列public int getQueue() {//先判斷隊(duì)列是否為空if (isEmpty()) {//為空就拋出異常,我們這里結(jié)束方法使用拋出異常方式throw new RuntimeException("隊(duì)列空,不能獲取數(shù)據(jù)~~~");}front++;//先將指針后移,//這里的取出并不是吧數(shù)組中的數(shù)據(jù)真正的取出,而且將指針后移,取出指針后移的這位數(shù)據(jù)//提現(xiàn)了先進(jìn)先出的隊(duì)列思想return arr[front];}//顯示隊(duì)列的所有數(shù)據(jù)public void showQueue() {//同樣先判斷隊(duì)列是否為空if (isEmpty()) {System.out.println("隊(duì)列空,沒(méi)有這個(gè)數(shù)據(jù)~~~");return;}//遍歷for (int i = 0; i < arr.length; i++) {System.out.println("arr[" + i + "]=" + arr[i]);}}//顯示隊(duì)列的頭數(shù)據(jù),不是取數(shù)劇public int headQueue() {if (isEmpty()) {//為空就拋出異常,我們這里結(jié)束方法使用拋出異常方式throw new RuntimeException("隊(duì)列空,沒(méi)有數(shù)據(jù)~~~");}//顯示是front指針當(dāng)前指的哪位數(shù)據(jù),因?yàn)榧偃邕€沒(méi)有從列隊(duì)中取出數(shù)據(jù),那么當(dāng)前就指向索引為0的位子,故為front+1 為0//若已經(jīng)取了索引為0的數(shù)據(jù),那么當(dāng)前指的就是索引為1的位子,故front+1 為1//若數(shù)據(jù)已經(jīng)取完,那么就判斷直接拋出異常不會(huì)到這一步,假設(shè)到了這一步,也會(huì)索引越界異常return arr[front + 1];}}

若看不懂,將代碼拷貝到idea中DEBUG看數(shù)據(jù)變化自然會(huì)懂

上面是線性的隊(duì)列,不能循環(huán)復(fù)用其中的排隊(duì)邏輯,當(dāng)隊(duì)列滿后,第一個(gè)走后,后來(lái)的不能加入子第一個(gè)位置,所以沒(méi)有達(dá)到復(fù)用效果
使用一些取模的方式達(dá)到讓線性的隊(duì)列轉(zhuǎn)換成環(huán)形隊(duì)列,從而實(shí)現(xiàn)先進(jìn)先出,后進(jìn)后出,循環(huán)環(huán)形隊(duì)列

數(shù)組模擬環(huán)形隊(duì)列

上述到達(dá)尾部又向前存儲(chǔ)的隊(duì)列稱為循環(huán)隊(duì)列，為了避免"假溢出"，我們通常采用循環(huán)隊(duì)列。

分析

一 尾索引的下一個(gè)為頭索引時(shí)表示隊(duì)列滿，即將隊(duì)列容量空出一個(gè)作為約定,這個(gè)在做判斷隊(duì)列滿的時(shí)候需要注意 (rear + 1) % maxSize == front 滿]

二 rear == front [空]

代碼實(shí)現(xiàn)環(huán)形隊(duì)列

package com.fs.demo_2020_07_11_queueArray;import java.util.Scanner;/*** 模擬環(huán)形隊(duì)列數(shù)組** 1.頭尾部指針取模重新計(jì)算指針值：(rear/front + 1) % maxSize* 2.隊(duì)列空的判斷邏輯：rear == front* 3.隊(duì)列滿的判斷邏輯：(rear + 1) % maxSize == front* 4.隊(duì)列內(nèi)有效數(shù)據(jù)個(gè)數(shù)：(rear - front + maxSize) % maxSize**/ public class CircleQueueArray {public static void main(String[] args) {//測(cè)試一把//創(chuàng)建一個(gè)隊(duì)列SimulationCircleQueueArray queue = new SimulationCircleQueueArray(4);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) {/*** 遍歷打印下每次執(zhí)完后數(shù)組中的數(shù)據(jù)*/int[] arr = queue.getArr();System.out.println("-------------------------------------------------");for (int i = 0; i < arr.length; i++) {int i1 = arr[i];System.out.println("arr數(shù)組索引:"+i+"位子當(dāng)前的數(shù)據(jù)為:"+i1+".");}System.out.println("-------------------------------------------------");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());e.printStackTrace();}break;case 'e': //退出scanner.close();loop = false;break;default:break;}}System.out.println("程序退出~~");} }//創(chuàng)建一個(gè)類(lèi)來(lái)模擬環(huán)形隊(duì)列數(shù)組 class SimulationCircleQueueArray{private int maxSize;//表示數(shù)字的最大容納量private int front;//模擬指針指向頭部數(shù)據(jù),對(duì)于普通的隊(duì)列做了調(diào)整,現(xiàn)在默認(rèn)指向第一個(gè)索引位子,也就是0private int rear;//模擬指針指向尾部數(shù)據(jù),同樣也是默認(rèn)指向第一個(gè)索引的位子,也就是0private int[] arr;//數(shù)組用于存放數(shù)據(jù),模擬隊(duì)列//提供一個(gè)get方法觀察數(shù)組中數(shù)據(jù)的變化public int[] getArr() {return arr;}/*** 創(chuàng)建環(huán)形隊(duì)列數(shù)組的構(gòu)造器** @param arrMaxSize 初始化這個(gè)環(huán)形隊(duì)列數(shù)組的容量*/public SimulationCircleQueueArray(int arrMaxSize) {maxSize = arrMaxSize;arr = new int[maxSize];//初始化數(shù)組的容量front = 0;rear = 0;}//判斷隊(duì)列數(shù)組是否滿了public boolean isFull() {/*判斷隊(duì)列是否滿環(huán)形隊(duì)列,判斷隊(duì)列滿,不僅僅在通過(guò)rear = maxSize -1 來(lái)判斷因?yàn)槭黔h(huán)形,尾部指針會(huì)回到之前的位子,所以通過(guò)取模來(lái)重新計(jì)算指針的值(rear+1)%maxSize == front;假設(shè)隊(duì)列內(nèi)部數(shù)組arr的最大容量為4隊(duì)列添加數(shù)據(jù)，rear指針需取模重新計(jì)算指針指向值：rear = (rear + 1) % maxSize，并通過(guò)(rear + 1) % maxSize == front來(lái)判斷隊(duì)列是否已滿1.隊(duì)列添加數(shù)據(jù)10，arr[0]=10，rear重新指向1，(1+1)%4!=0，隊(duì)列未滿2.隊(duì)列添加數(shù)據(jù)20，arr[1]=20，rear重新指向2，(2+1)%4!=0，隊(duì)列未滿3.隊(duì)列添加數(shù)據(jù)30，arr[2]=30，rear重新指向3，(3+1)%4==0，隊(duì)列滿，不能再添加數(shù)據(jù)此時(shí)，隊(duì)列內(nèi)所有數(shù)據(jù)為：arr[0]=10,arr[1]=20,arr[2]=30，隊(duì)列有效數(shù)據(jù)個(gè)數(shù)：(3-0+4)%4=3*/return (rear+1)%maxSize == front;}//判斷隊(duì)列是否為空public boolean isEmpty() {/*隊(duì)列當(dāng)取得指針和添加的指針一致的時(shí)候,所明去完了,沒(méi)有數(shù)據(jù)*/return rear == front;}//添加數(shù)據(jù)到隊(duì)列public void addQueue(int data) {/*隊(duì)列的添加:一般線性隊(duì)列,尾部指針直接遞增而環(huán)形隊(duì)列,尾部指針可能在次指向索引為0的位子,因此不能單一的通過(guò)遞增來(lái)處理,需要取模重新計(jì)算尾部的指針位置*///添加前先判斷隊(duì)列是否滿了if (isFull()) {System.out.println("隊(duì)列滿,不能加入數(shù)據(jù)~~~");return;}arr[rear] = data;//在尾部指針指向的位子添加傳遞的數(shù)據(jù)//添加值后,尾部指針的走向不能在++遞增來(lái)實(shí)現(xiàn),需要從新取模運(yùn)算rear = (rear + 1)%maxSize;}//獲取隊(duì)列的數(shù)據(jù),出隊(duì)列public int getQueue() {/*環(huán)形列隊(duì)取數(shù)據(jù):和添加數(shù)據(jù)一樣,添加是尾部指針不能一直遞增,需要取模重新計(jì)算尾部指針的位子而頭部指針在每次取出數(shù)據(jù)后也不能一直遞增,需要取模讓指針回到最初的位子*///先判斷隊(duì)列是否為空if (isEmpty()) {//為空就拋出異常,我們這里結(jié)束方法使用拋出異常方式throw new RuntimeException("隊(duì)列空,不能獲取數(shù)據(jù)~~~");}//先獲取到頭部指針指向的索引位子獲取出數(shù)據(jù)int value = arr[front];//對(duì)取模計(jì)算出下一次頭部指針的位子front = (front + 1) % maxSize;//將數(shù)據(jù)返回return value;}/*** 顯示隊(duì)列所有的數(shù)據(jù)*/public void showQueue() {if (isEmpty()) {System.out.println("隊(duì)列為空，無(wú)法顯示隊(duì)列的全部數(shù)據(jù)");return;}// 遍歷數(shù)組// 不能單一的對(duì)角標(biāo)遞增處理，會(huì)出現(xiàn)角標(biāo)越界異常// 應(yīng)對(duì)環(huán)形隊(duì)列內(nèi)部的有效數(shù)據(jù)，從頭部數(shù)據(jù)開(kāi)始遍歷依次取出// 有效數(shù)據(jù)的下標(biāo)：i % maxSizefor (int i = front; i < front + size(); i++) {System.out.printf("arr[%d] = %d\n", i % maxSize, arr[i % maxSize]);}}/*** 獲取隊(duì)列有效數(shù)據(jù)的個(gè)數(shù)* @return 隊(duì)列有效數(shù)據(jù)的個(gè)數(shù)*/private int size() {return (rear - front + maxSize) % maxSize;}//顯示隊(duì)列的頭數(shù)據(jù),不是取數(shù)據(jù)public int headQueue() {/*獲取列隊(duì)頭部數(shù)據(jù)就是獲取頭部指針指向的位子*/if (isEmpty()) {//為空就拋出異常,我們這里結(jié)束方法使用拋出異常方式throw new RuntimeException("隊(duì)列空,沒(méi)有數(shù)據(jù)~~~");}return arr[front];} }

代碼運(yùn)行控制臺(tái)測(cè)試

D:\Java\JDK\java1.8 ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:0. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:0. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:0. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:0. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù) a 輸出一個(gè)數(shù) 10 ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:10. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:0. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:0. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:0. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù) a 輸出一個(gè)數(shù) 20 ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:10. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:20. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:0. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:0. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù) a 輸出一個(gè)數(shù) 30 ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:10. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:20. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:30. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:0. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù) s arr[0] = 10 arr[1] = 20 arr[2] = 30 ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:10. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:20. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:30. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:0. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù) g 取出的數(shù)據(jù)是10 ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:10. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:20. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:30. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:0. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù) s arr[1] = 20 arr[2] = 30 ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:10. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:20. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:30. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:0. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù) g 取出的數(shù)據(jù)是20 ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:10. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:20. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:30. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:0. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù) s arr[2] = 30 ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:10. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:20. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:30. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:0. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù) h 隊(duì)列頭的數(shù)據(jù)是30 ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:10. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:20. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:30. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:0. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù) g 取出的數(shù)據(jù)是30 ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:10. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:20. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:30. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:0. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù) h java.lang.RuntimeException: 隊(duì)列空,沒(méi)有數(shù)據(jù)~~~at com.fs.demo_2020_07_11_queueArray.SimulationCircleQueueArray.headQueue(CircleQueueArray.java:203)at com.fs.demo_2020_07_11_queueArray.CircleQueueArray.main(CircleQueueArray.java:60) ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:10. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:20. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:30. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:0. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù) s 隊(duì)列為空，無(wú)法顯示隊(duì)列的全部數(shù)據(jù) ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:10. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:20. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:30. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:0. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù) a 輸出一個(gè)數(shù) 40 ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:10. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:20. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:30. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:40. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù) a 輸出一個(gè)數(shù) 50 ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:50. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:20. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:30. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:40. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù) a 輸出一個(gè)數(shù) 60 ------------------------------------------------- arr數(shù)組索引:0位子當(dāng)前的數(shù)據(jù)為:50. arr數(shù)組索引:1位子當(dāng)前的數(shù)據(jù)為:60. arr數(shù)組索引:2位子當(dāng)前的數(shù)據(jù)為:30. arr數(shù)組索引:3位子當(dāng)前的數(shù)據(jù)為:40. ------------------------------------------------- s(show): 顯示隊(duì)列 e(exit): 退出程序 a(add): 添加數(shù)據(jù)到隊(duì)列 g(get): 從隊(duì)列取出數(shù)據(jù) h(head): 查看隊(duì)列頭的數(shù)據(jù)

環(huán)形隊(duì)列的解釋

下面解釋來(lái)源于網(wǎng)絡(luò)收集
作者：rainchxy
鏈接：https://www.jianshu.com/p/9ba8a65464dd
來(lái)源：簡(jiǎn)書(shū)

為什么要%Maxsize呢？

主要是為了處理臨界狀態(tài)，即Q.rear向后移動(dòng)一個(gè)位置Q.rear+1后，很有可能超出了數(shù)組的下標(biāo)，這時(shí)它的下一個(gè)位置其實(shí)是0，如果將一維數(shù)組畫(huà)成環(huán)形圖，如圖所示：

上圖中最大空間Maxsize，當(dāng)Q.rear=Maxsize-1時(shí)，(Q.rear+1)%Maxsize=0，而且Q.front=0，正好滿足隊(duì)滿的條件：(Q.rear+1) %Maxsize= Q.front，此時(shí)為隊(duì)滿。

因此無(wú)論是front還是rear向后移動(dòng)一個(gè)位置時(shí)，都要加1與最大空間Maxsize取模運(yùn)算，處理臨界問(wèn)題。

總結(jié)：

隊(duì)空：Q.front=Q.rear; // Q.rear和Q.front指向同一個(gè)位置

隊(duì)滿： (Q.rear+1) %Maxsize=Q.front; // Q.rear向后移一位正好是Q.front

入隊(duì)：

Q.base[Q.rear]=x; //將元素放入Q.rear所指空間，

Q.rear =( Q.rear+1) %Maxsize; // Q.rear向后移一位

出隊(duì)：

e= Q.base[Q.front]; //用變量記錄Q.front所指元素，

Q.front=(Q.front+1) %Maxsize // Q. front向后移一位

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