C++面向對象程序設計雙語教程（第3版）-參考答案 劉嘉敏 【ch07】Polymorphism and Virtual Functions

Chapter7PolymorphismandVirtualFunctions1.Writetheoutputofthefollowingprogram.略。2.Writetheoutputofthefollowingprogram.略。3.GiventhedefinitionofaPersonclassasfollows:DesignthetwoclassesStudentandTeacher.TheyarederivedfromclassPerson.(1)ClassStudenthasthepropertiesofname,id,classNoandstudyTimeperweek;ClassTeacherhasthepropertiesofname,id,departmentandworkTimeperweek.(2)Calculatethework/studenttime.Calculatingmethodsaredefinedasfollows:Thestudytimeofastudentistheclassquantitymultipliedby2(hour)perweek;Theworktimeofateacheristheteachingquantitymultiplied2(hour)perweek.(3)DisplaytheinformationforclassesStudentandTeacher.```cpp#include<iostream>#include<string>usingnamespacestd;classPerson{protected:stringname;longid;public:Person(string_name,long_id):name(_name),id(_id){}stringgetName()const{returnname;}longgetId()const{returnid;}};classStudent:publicPerson{private:stringclassName;intstudyTime;public:Student(string_name,long_id,string_className,int_studyTime):Person(_name,_id),className(_className),studyTime(_studyTime){}intgetStudyTime()const{returnstudyTime;}intcalculateWorkTime()const{returnstudyTime*2;}//計算學生的學習時間};classTeacher:publicPerson{private:stringdepartment;intteachingQuantity;public:Teacher(string_name,long_id,string_department,int_teachingQuantity):Person(_name,_id),department(_department),teachingQuantity(_teachingQuantity){}intgetTeachingQuantity()const{returnteachingQuantity;}intcalculateWorkTime()const{returnteachingQuantity*2;}//計算教師的工作時間};intmain(){//創(chuàng)建學生對象Studentstudent(\張三\1234567890,\三年級一班\10);//創(chuàng)建教師對象Teacherteacher(\李四\9876543210,\數(shù)學系\5);//輸出學生和教師的信息cout<<\學生姓名:\<<student.getName()<<endl;cout<<\學生身份證:\<<student.getId()<<endl;cout<<\學生班級:\<<student.getClassName()<<endl;cout<<\學生學習時間:\<<student.getStudyTime()<<\小時/周\<<endl;cout<<\學生工作時間:\<<student.calculateWorkTime()<<\小時/周\<<endl;cout<<endl;cout<<\教師姓名:\<<teacher.getName()<<endl;cout<<\教師身份證:\<<teacher.getId()<<endl;cout<<\教師部門:\<<teacher.getDepartment()<<endl;cout<<\教師教學數(shù)量:\<<teacher.getTeachingQuantity()<<\節(jié)/周\<<endl;cout<<\教師工作時間:\<<teacher.calculateWorkTime()<<\小時/周\<<endl;return0;}```在這個程序中，`Person`類是學生和教師類的基類，包含姓名和身份證號兩個屬性。`Student`和`Teacher`類分別繼承于`Person`類，并新增了自己的屬性和方法。`Student`類有一個額外的屬性`className`表示班級，和`studyTime`表示每周學習時間。`calculateWorkTime`方法用于計算學生的工作時間，即學習時間乘以2。`Teacher`類有一個額外的屬性`department`表示部門，和`teachingQuantity`表示每周教學數(shù)量。`calculateWorkTime`方法用于計算教師的工作時間，即教學數(shù)量乘以2。在程序的`main`函數(shù)中，我們創(chuàng)建了一個學生對象和一個教師對象，并打印出他們的信息以及計算出的工作/學習時間。4.GiventhedefinitionofclassPointasfollows:DesignaCircleclasswiththepropertiesofacenterandaradius.Thecenterofthecirclcisapoint.TheCircleclassmustbederivedfromthePointclass.TheCircleclasscanimplementtheoperationsofcalculatingtheareaandprintingoutthecenter,radiusandarea.DesignanotherclassCylinderwiththepropertiesofabaseandaheight.Thebaseisacircle.DerivethisclassfromtheCircleclass.TheCylinderclasscanimplementtheoperationsofcalculatingthevolume,andprintingoutthebase,heightandvolume.Supposethefollowingcodeisinthemainfunction.```pythonimportmathclassPoint:def__init__(self,x=0,y=0):self.x=xself.y=yclassCircle(Point):def__init__(self,center,radius):super().__init__(center.x,center.y)self.radius=radiusdefarea(self):returnmath.pi*self.radius**2defprint_details(self):print(\CircleDetails:\print(\Center:({},{})\format(self.x,self.y))print(\Radius:{}\format(self.radius))print(\Area:{:.2f}\format(self.area()))classCylinder(Circle):def__init__(self,base_center,radius,height):super().__init__(base_center,radius)self.height=heightdefvolume(self):returnself.area()*self.heightdefprint_details(self):print(\CylinderDetails:\print(\BaseCenter:({},{})\format(self.x,self.y))print(\Radius:{}\format(self.radius))print(\Height:{}\format(self.height))print(\Volume:{:.2f}\format(self.volume()))#Exampleusage:if__name__=='__main__':c=Circle(Point(0,0),3)c.print_details()print()cy=Cylinder(Point(2,2),3,5)cy.print_details()```Thiscodedefinesa`Point`classasthebaseclass,`Circle`classderivedfrom`Point`,and`Cylinder`classderivedfrom`Circle`.The`Circle`classcalculatestheareaandprintsthedetailsofacircle,whilethe`Cylinder`classcalculatesthevolumeandprintsthedetailsofacylinder.The`main`functiondemonstratestheusageoftheseclassesbycreatingobjectsandcallingtheirrespectivemethods.5.Giventhefollowingcode:(1)CompletethedefmitionofclassEmployee.Note:employee'spayment=payRate*hoursWorked.(2)DefimeaManagerclassderivedfromclassEmployee.IthasthemembersofEmploveeanditsownmemberlevel.Note:manager'spayment=payRate*level*hoursWorked.(3)DefineanotherclassSalesmanderivedfromclassEmployee.ItalsohasthemembersofEmployee,inadditiontoitsownmembersale.Note:salesman'spayment=payRate*sale*hoursWorked.(4)TesttheManagerandSalesmanclassesbyusingabaseclasspointer.```cpp#include<iostream>usingnamespacestd;classEmployee{protected:intlevel;floatsalary;intworkHours;public:Employee(intl,floats,inth):level(l),salary(s),workHours(h){}virtualvoidcalculatePayment(){floatpayment=salary*workHours;cout<<\Employee'spayment:$\<<payment<<endl;}voiddemote(){if(level>1){level--;}cout<<\Employee'sleveldemotedto:\<<level<<endl;}};classManager:publicEmployee{private:stringemployer;public:Manager(intl,floats,inth,stringe):Employee(l,s,h),employer(e){}voidcalculatePayment(){floatpayment=salary*level*workHours;cout<<\Manager'spayment:$\<<payment<<endl;}};classSalesperson:publicEmployee{private:intsales;public:Salesperson(intl,floats,inth,intsa):Employee(l,s,h),sales(sa){}voidcalculatePayment(){floatpayment=salary*workHours+sales*0.1;cout<<\Salesperson'spayment:$\<<payment<<endl;}};intmain(){Employeeemployee(3,20,8);Managermanager(5,30,8,\ABCCompany\Salespersonsalesperson(3,15,8,1000);employee.calculatePayment();manager.calculatePayment();salesperson.calculatePayment();employee.demote();return0;}```這段代碼定義了一個基類Employee，以及從該類派生的Manager和Salesperson類。Employee類有級別、工資和工作時間的成員變量，以及計算支付和降級的成員函數(shù)。Manager類還有一個雇主成員變量，并重寫了計算支付的函數(shù)。Salesperson類還有銷售額成員變量，并也重寫了計算支付的函數(shù)。在主函數(shù)中，示例了如何創(chuàng)建員工、經理和銷售員對象，并調用它們的計算支付函數(shù)和降級函數(shù)。輸出會顯示出每個類的支付金額，以及員工降級后的級別。6.Hereisaclasshierarchy,showninFigure7-5,torepresentvariousmediaobjects:GiventhedefinitionofthebaseclassMedia:(1)Explaintheclassrelationshipdescribedinthehierarchydiagram.(2)DefinetheBookandMagazineclassesaccordingtothehierarchydiagram.(Hint:Theprintfunctionofeachclassdisplaysallinformationofdatamembers.Theidfunctionofeachclassreturnsastringidentifierthatcanindicatethemediafeature.Thisidentifierconsistsofdatamembersofeachclass)(3)WritethemainfunctiontotesttheBookandMagazineclasses.(Hint:YoumustdefineapointertoaMediaobjectinthemainfunction.)略。7.DesignsaclassnamedPersonanditsderivedclassesnamedStudentandEmployee.AssumethatthedeclarationofthePersonclassisasfollows:(1)DefinethetoStringfunctioninthePersonclass.ThereturningvalueofthetoStringfunctionisusedtodisplaytheclassinformationinthefollowingformat:Name:XXXX;Address:XXXXXXX.(2)DefinetheStudentclassderivedfromthePersonclass.Astudenthasaclassstatus(freshmen,sophomore,junior,orsenior).OverridethetoStringfunctionintheStudentclass.(3)DefinetheEmployeeclassderivedfromthePersonclass.Anemployeehasanofficeandasalary.OverridethetoStringfunctionintheEmployeeclass.(4)WriteatoplevelfunctionwithaparameterofPersontypeandwritethemainfunctiontotesttheStudentandEmployeeclasses.```cpp#include<iostream>usingnamespacestd;classPerson{protected:stringname;stringaddress;public:Person(stringname=\stringaddress=\{this->name=name;this->address=address;}stringtoString(){return\Name:\+name+\;\地址:\+address+\}};classStudent:publicPerson{private:intstudentID;public:Student(stringname=\stringaddress=\intstudentID=0):Person(name,address){this->studentID=studentID;}};intmain(){Personperson(\John\\123MainSt\Studentstudent(\Alice\\456ElmSt\12345);cout<<\Person:\<<endl;cout<<person.toString()<<endl;cout<<Student:\<<endl;cout<<student.toString()<<endl;return0;}```這段代碼定義了一個名為\Person\的基類及其名為\Student\的派生類。Person類有一個toString函數(shù)，用于返回格式化的類信息。Student類從Person類派生而來，并添加了一個名為studentID的新成員。在主函數(shù)中，我們創(chuàng)建了一個Person對象和一個Student對象，并分別輸出它們的類信息。運行該程序，你將得到類似以下的輸出結果：```Person:Name:John;地址:123MainSt.Student:Name:Alice;地址:456ElmSt.8.Writeaprogram.(1)AbstractbaseclassShape.(2)ClassesTriangle,SquareandCirclearederivedfromShape.(3)CalculatetheareasandperimetersofTriangle,SquareandCircle.下面是一個使用C++編寫的示例程序，實現(xiàn)了抽象基類Shape和派生類Triangle、Square和Circle的功能。每個形狀類都可以計算自身的面積和周長。請注意，代碼中的計算公式可能需要根據實際情況進行更改。```cpp#include<iostream>usingnamespacestd;//抽象的基類形狀classShape{public://純虛函數(shù)，用于計算面積virtualfloatgetArea()=0;//純虛函數(shù)，用于計算周長virtualfloatgetPerimeter()=0;};//類三角形，從形狀派生classTriangle:publicShape{private:floatbase;floatheight;public://構造函數(shù)Triangle(floatbase,floatheight){this->base=base;this->height=height;}//重寫計算面積的函數(shù)floatgetArea()override{return0.5*base*height;}//重寫計算周長的函數(shù)floatgetPerimeter()override{//假設三角形的邊長相等return3*base;}};//類方形，從形狀派生classSquare:publicShape{private:floatside;public://構造函數(shù)Square(floatside){this->side=side;}//重寫計算面積的函數(shù)floatgetArea()override{returnside*side;}//重寫計算周長的函數(shù)floatgetPerimeter(){return4*side;}};//類圓形，從形狀派生classCircle:publicShape{private:floatradius;constfloatpi=3.14159;//假設圓周率為3.14159public://構造函數(shù)Circle(floatradius){this->radiusradius;}//重寫計算面積的函數(shù)floatgetArea()override{returnpi*radius*radius;}//重寫計算周長的函數(shù)floatgetPerimeter()override{return2*pi*radius;}};intmain(){//創(chuàng)建三個形狀對象Triangletriangle(5,8);Squaresquare(4);Circlecircle(3);//輸出每個形狀的面積和周長cout<<\Triangle:Area=\<<triangle.getArea()<<\Perimeter=\<<triangle.getPerimeter()<<endl;cout<<\Square:Area=\<<square.getArea()<<\Perimeter=\<<square.getPerimeter()<<endl;cout<<\Circle:Area=\<<circle.getArea()<<\Perimeter=\<<circle.getPerimeter()<<endl;return0;}```這個程序定義了一個抽象基類Shape，以及派生類Triangle、Square和Circle。每個派生類實現(xiàn)了Shape基類中的純虛函數(shù)getArea()和getPerimeter()，并提供了自己的實現(xiàn)。在主函數(shù)中，我們創(chuàng)建了一個Triangle對象、一個Square對象和一個Circle對象，并使用它們的成員函數(shù)分別計算和輸出面積和周長。9.Designaclasshierarchyasfollows;(1)AbaseclassShapewithvirtualfunctionprint.(2)ClassesTwoDShapeandThreeDShapederivedfromShape.TivoDShapehasvirtualfunctionsareaandperimeter:ThreeDShapehasvirtualfunctionvolume.(3)ClassesTriangle,SquareandCirclearederivedfromTwoDShape.(4)ClassesCube,CuboidandSpherearederivedfromThreeDShape.Overridethedefinitionoftheprintfunctionofeachderivedclass.Testthehierarchybyusingthemainfunctionandatop-levelfunctionwithapointertoclassShape.```cpp#include<iostream>usingnamespacestd;//基類形狀classShape{public:virtualvoidprint()=0;//虛擬函數(shù)打印};//二維形狀類classTwoDShape:publicShape{public:virtualfloatarea()=0;//虛擬函數(shù)計算面積virtualfloatperimeter()=0;//虛擬函數(shù)計算周長};//三維形狀類classThreeDShape:publicShape{public:virtualf