普通队列
无fuck可speak
package com.whb.queue;
import java.util.Scanner;
public class ArrayQueueDemo {
public static void main(String[] args) {
//测试一把
//创建一个队列
ArrayQueue queue = 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);//接收一个字符
switch (key) {
case 's':
queue.showQueue();
break;
case 'a':
System.out.println("输出一个数");
int value = scanner.nextInt();
queue.addQueue(value);
break;
case 'g': //取出数据
try {
int res = queue.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': //查看队列头的数据
try {
int res = queue.headQueue();
System.out.printf("队列头的数据是%d\n", res);
} catch (Exception e) {
// TODO: handle exception
System.out.println(e.getMessage());
}
break;
case 'e': //退出
scanner.close();
loop = false;
break;
default:
break;
}
}
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;
rear = -1;
}
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,不能加入数据");
return;
}
rear++;
arr[rear] = n;
}
public int getQueue(){
if(isEmpty()){
throw new RuntimeException("队列为空");
}else if(front==rear){
throw new RuntimeException("数据已经取完");
}
front++;
return arr[front];
}
public void showQueue(){
if(isEmpty()){
System.out.println("空");
return;
}
for (int i = 0; i < arr.length; i++){
System.out.printf("arr[%d]=%d\n", i, arr[i]);
}
}
public int headQueue(){
if(isEmpty()){
throw new RuntimeException("空");
}
return arr[front+1];
}
}
环形队列
实现环形队列时,front指向队列头部的数据,rear指向最后一个数据的后面,空出来一个用于平衡rear,即指定大小为4时,实际只能存储3个数据
判断为空:
当front和rear指向同一个数据时,表示未存储数据或者数据已经取完
判断满:rear执向末尾数据的下一个位置,当要向队列里边添加数据时rear需要向后移动,如果rear要移动的下一个位置恰好是front头部指向的数据时,表示队列已经满了 即:(rear + 1) % maxSize == front
size的判别:当rear大于front时,size = rear - front,由于是环形队列,所以rear可能小于front,当rear小于front时,size = maxsize - (rear到front之间空出来的大小) 即：size = maxsize - (front - rear) = maxsize + rear - front
Size
空
满
可以看到满之后也会空一个数据位置
package com.whb.queue;
import java.util.Scanner;
public class CircleArrayQueueDemo {
public static void main(String[] args) {
//测试一把
System.out.println("测试数组模拟环形队列的案例~~~");
// 创建一个环形队列
CircleArray queue = new CircleArray(4); //说明设置4, 其队列的有效数据最大是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);// 接收一个字符
switch (key) {
case 's':
queue.showQueue();
break;
case 'a':
System.out.println("输出一个数");
int value = scanner.nextInt();
queue.addQueue(value);
break;
case 'g': // 取出数据
try {
int res = queue.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': // 查看队列头的数据
try {
int res = queue.headQueue();
System.out.printf("队列头的数据是%d\n", res);
} catch (Exception e) {
// TODO: handle exception
System.out.println(e.getMessage());
}
break;
case 'e': // 退出
scanner.close();
loop = false;
break;
default:
break;
}
}
System.out.println("程序退出~~");
}
}
class CircleArray{
private int maxSize;
private int front;
private int rear;
private int[] arr;
public CircleArray(int arrMaxSizr){
maxSize = arrMaxSizr;
arr = new int[maxSize];
}
public int size(){
return (rear + maxSize - front) % maxSize;
}
// 判断队列是否满
public boolean isEmpty(){
return rear == front;
}
public boolean isFull(){
return (rear+1)%maxSize == front;
}
public void addQueue(int n){
if(isFull()){
System.out.println("满");
return;
}
arr[rear] = n;
rear = (rear+1)%maxSize;
}
public int getQueue(){
if(isEmpty()){
throw new RuntimeException("队列空，不能取数据");
}
int value = arr[front];
front = (front + 1) % maxSize;
return value;
}
public void showQueue(){
if(isEmpty()){
System.out.println("empty");
return;
}
for (int i = front; i < front + size();i++){
System.out.printf("arr[%d]=%d\n", i % maxSize, arr[i % maxSize]);
}
}
// 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];
}
}