class Queue:
    def __init__(self):
        self.items = []            # 構(gòu)建空隊(duì)列
    def isEmpty(self):
        return self.items ==[]     # 判斷是否為空
    def enqueue(self,item):
        self.items.insert(0, item) # 在隊(duì)列尾部(列表左端)插入元素
    def dequeue(self):
        return self.items.pop()    # 在隊(duì)列頭部(列表右端)移出元素
    def size(self):
        return len(self.items)     # 隊(duì)列(列表)長(zhǎng)度

import random
# 模擬打印機(jī)
class Printer:
    # 打印機(jī)初始化
    def __init__(self, ppm):
        self.pagerate = ppm      # 打印速度 頁(yè)/分鐘
        self.currentTask = None  # 現(xiàn)有任務(wù)
        self.timeRemain = 0      # 該任務(wù)所需時(shí)間
    # 打印任務(wù)倒計(jì)時(shí) 0代表打印完成
    def tick(self):
        # 如果打印機(jī)正在執(zhí)行任務(wù)
        if self.currentTask != None:
            # 該任務(wù)執(zhí)行時(shí)間 = 執(zhí)行時(shí)間 - 1（執(zhí)行時(shí)間倒計(jì)時(shí)）
            self.timeRemaining = self.timeRemaining - 1   
            if self.timeRemaining <= 0:     # 該任務(wù)執(zhí)行時(shí)間 <= 0
                self.currentTask = None     # 該任務(wù)執(zhí)行完畢
    # 判斷打印機(jī)是否空閑
    def busy(self):
        if self.currentTask != None:
            return True
        else:
            return False
    # 打印機(jī)接受新任務(wù)
    def startNext(self, newtask):
        self.currentTask = newtask
        # 新打印任務(wù)需要時(shí)間 = 新任務(wù)頁(yè)數(shù) * (60 / 每分鐘打印多少頁(yè)的速度)
        # (60 / 每分鐘打印多少頁(yè)的速度) = 每打印一頁(yè)所需要的秒數(shù)
        self.timeRemaining = newtask.getPages() * (60 / self.pagerate)

# 模擬單個(gè)任務(wù)的屬性
class Task:
    # 任務(wù)初始化
    def __init__(self, time):
        self.timestamp = time                # 創(chuàng)建任務(wù)的時(shí)間點(diǎn)
        self.pages = random.randrange(1, 21) # 任務(wù)頁(yè)數(shù) 在 1~20 間隨機(jī)生成
    def getStamp(self):
        return self.timestamp  # 獲取任務(wù)創(chuàng)建的時(shí)間點(diǎn)
    def getPages(self):
        return self.pages      # 獲取任務(wù)的頁(yè)數(shù)
    def waitTime(self, currenttime):
        # 任務(wù)的等待時(shí)間 = 當(dāng)前時(shí)間 - 任務(wù)創(chuàng)建的時(shí)間點(diǎn)
        return currenttime - self.timestamp   

# 模擬學(xué)生創(chuàng)建的新打印請(qǐng)求
def newPrintTask():
    # 打印請(qǐng)求是一個(gè)隨機(jī)事件
    # 通過(guò)1~180之間的一個(gè)隨機(jī)數(shù)來(lái)模擬每秒內(nèi)產(chǎn)生打印請(qǐng)求的概率
    # 如果隨機(jī)數(shù)正好是180，那么就認(rèn)為有一個(gè)打印請(qǐng)求被創(chuàng)建。
    num = random.randrange(1, 181)
    if num == 180:
        return True
    else:
        return False

# 模擬打印過(guò)程
def simulation(numSeconds, pagesPerMinute):
    labprinter = Printer(pagesPerMinute)
    printQueue = Queue()
    waitingtimes = []
    for currentSecond in range(numSeconds):
        if newPrintTask():
            task = Task(currentSecond)
            printQueue.enqueue(task)
        if(not labprinter.busy())and(not printQueue.isEmpty()):
            nexttask = printQueue.dequeue()
            waitingtimes.append(nexttask.waitTime(currentSecond))
            labprinter.startNext(nexttask)
        labprinter.tick()
    averageWait = sum(waitingtimes)/len(waitingtimes)
    print("平均等待 %6.2f 秒，還有 %3d 個(gè)任務(wù)等待處理"
          % (averageWait, printQueue.size()))

def simulation(numSeconds, pagesPerMinute):
    # numSeconds-時(shí)間段
    # pagesPerMinute-打印速度，頁(yè)/分鐘
    labprinter = Printer(pagesPerMinute)  # 創(chuàng)建打印機(jī)
    printQueue = Queue()                  # 創(chuàng)建打印機(jī)任務(wù)隊(duì)列
    waitingtimes = []                     # 創(chuàng)建等待時(shí)間數(shù)據(jù)樣本列表
    for currentSecond in range(numSeconds):  # 一次循環(huán)代表一秒
        if newPrintTask():                   # 如果 有打印請(qǐng)求創(chuàng)建
            task = Task(currentSecond)       # 創(chuàng)建打印任務(wù)并記錄當(dāng)前時(shí)間點(diǎn)
            printQueue.enqueue(task)         # 打印任務(wù)進(jìn)入打印機(jī)任務(wù)隊(duì)列
        # 如果 打印機(jī)空閑 并且 打印機(jī)任務(wù)隊(duì)列有任務(wù)
        if(not labprinter.busy())and(not printQueue.isEmpty()):
            nexttask = printQueue.dequeue()  # 從隊(duì)列取出新任務(wù)
            # 根據(jù)當(dāng)前時(shí)間點(diǎn)計(jì)算新任務(wù)在任務(wù)隊(duì)列里的等待時(shí)間 并將等待時(shí)間記錄進(jìn)樣本列表
            waitingtimes.append(nexttask.waitTime(currentSecond))
            labprinter.startNext(nexttask)   # 開始執(zhí)行新任務(wù) 打印機(jī)進(jìn)入忙碌狀態(tài)
        labprinter.tick()  # 每循環(huán)一次 當(dāng)前打印任務(wù)執(zhí)行倒計(jì)時(shí)減少一秒
    averageWait = sum(waitingtimes)/len(waitingtimes)
    print("平均等待 %6.2f 秒，還有 %3d 個(gè)任務(wù)等待處理" % (averageWait, printQueue.size()))