第三章习题答案 // include definition of class GradeBook from GradeBook.h #include "GradeBook.h"

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1 第三章习题答案 3.11 // Exercise 3.11 Solution: GradeBook.h // Definition of GradeBook class that stores an instructor's name. #include <string> // program uses C++ standard string class using std::string; // GradeBook class definition class GradeBook public: // constructor initializes course name and instructor name GradeBook( string, string ); void setcoursename( string ); // function to set the course name string getcoursename(); // function to retrieve the course name void setinstructorname( string ); // function to set instructor name string getinstructorname(); // function to retrieve instructor name void displaymessage(); // display welcome message and instructor name private: string coursename; // course name for this GradeBook string instructorname; // instructor name for this GradeBook }; // end class GradeBook // Exercise 3.11 Solution: GradeBook.cpp // Member-function definitions for class GradeBook. // include definition of class GradeBook from GradeBook.h #include "GradeBook.h" // constructor initializes coursename and instructorname // with strings supplied as arguments GradeBook::GradeBook( string course, string instructor ) setcoursename( course ); // initializes coursename setinstructorname( instructor ); // initializes instructorname } // end GradeBook constructor // function to set the course name

2 void GradeBook::setCourseName( string name ) coursename = name; // store the course name } // end function setcoursename // function to retrieve the course name string GradeBook::getCourseName() return coursename; } // end function getcoursename // function to set the instructor name void GradeBook::setInstructorName( string name ) instructorname = name; // store the instructor name } // end function setinstructorname // function to retrieve the instructor name string GradeBook::getInstructorName() return instructorname; } // end function getinstructorname // display a welcome message and the instructor's name void GradeBook::displayMessage() // display a welcome message containing the course name cout << "Welcome to the grade book for\n" << getcoursename() << "!" << endl; // display the instructor's name cout << "This course is presented by: " << getinstructorname() << endl; } // end function displaymessage // Exercise 3.11 Solution: ex03_11.cpp // Test program for modified GradeBook class. // include definition of class GradeBook from GradeBook.h #include "GradeBook.h" // function main begins program execution

3 int main() // create a GradeBook object; pass a course name and instructor name GradeBook gradebook( "CS101 Introduction to C++ Programming", "Professor Smith" ); // display initial value of instructorname of GradeBook object cout << "gradebook instructor name is: " << gradebook.getinstructorname() << "\n\n"; // modify the instructorname using set function gradebook.setinstructorname( "Assistant Professor Bates" ); // display new value of instructorname cout << "new gradebook instructor name is: " << gradebook.getinstructorname() << "\n\n"; // display welcome message and instructor's name gradebook.displaymessage(); return 0; // indicate successful termination } // end main 3.13 // Exercise 3.13 Solution: Invoice.h // Definition of Invoice class that represents an invoice // for an item sold at a hardware store. #include <string> // program uses C++ standard string class using std::string; // Invoice class definition class Invoice public: // constructor initializes the four data members Invoice( string, string, int, int ); // set and get functions for the four data members void setpartnumber( string ); // part number string getpartnumber(); void setpartdescription( string ); // part description string getpartdescription(); void setquantity( int ); // quantity int getquantity();

4 void setpriceperitem( int ); // price per item int getpriceperitem(); // calculates invoice amount by multiplying quantity x price per item int getinvoiceamount(); private: string partnumber; // the number of the part being sold string partdescription; // description of the part being sold int quantity; // how many of the items are being sold int priceperitem; // price per item }; // end class Invoice // Exercise 3.13 Solution: Invoice.cpp // Member-function definitions for class Invoice. // include definition of class Invoice from Invoice.h #include "Invoice.h" // Invoice constructor initializes the class's four data members Invoice::Invoice( string number, string description, int count, int price ) setpartnumber( number ); // store partnumber setpartdescription( description ); // store partdescription setquantity( count ); // validate and store quantity setpriceperitem( price ); // validate and store priceperitem } // end Invoice constructor // set part number void Invoice::setPartNumber( string number ) partnumber = number; // no validation needed } // end function setpartnumber // get part number string Invoice::getPartNumber() return partnumber; } // end function getpartnumber

5 // set part description void Invoice::setPartDescription( string description ) partdescription = description; // no validation needed } // end function setpartdescription // get part description string Invoice::getPartDescription() return partdescription; } // end function getpartdescription // set quantity; if not positive, set to 0 void Invoice::setQuantity( int count ) if ( count > 0 ) // if quantity is positive quantity = count; // set quantity to count if ( count <= 0 ) // if quantity is not positive quantity = 0; // set quantity to 0 cout << "\nquantity cannot be negative. quantity set to 0.\n"; } // end if } // end function setquantity // get quantity int Invoice::getQuantity() return quantity; } // end function getquantity // set price per item; if not positive, set to 0 void Invoice::setPricePerItem( int price ) if ( price > 0 ) // if price is positive priceperitem = price; // set priceperitem to price if ( price <= 0 ) // if price is not positive priceperitem = 0; // set priceperitem to 0 cout << "\npriceperitem cannot be negative. " << "priceperitem set to 0.\n"; } // end if } // end function setpriceperitem

6 // get price per item int Invoice::getPricePerItem() return priceperitem; } // end function getpriceperitem // calulates invoice amount by multiplying quantity x price per item int Invoice::getInvoiceAmount() return getquantity() * getpriceperitem(); } // end function getinvoiceamount // Exercise 3.13 Solution: ex03_13.cpp // Create and manipulate an Invoice object. using std::cin; // include definition of class Invoice from Invoice.h #include "Invoice.h" // function main begins program execution int main() // create an Invoice object Invoice invoice( "12345", "Hammer", 100, 5 ); // display the invoice data members and calculate the amount cout << "Part number: " << invoice.getpartnumber() << endl; cout << "Part description: " << invoice.getpartdescription() << endl; cout << "Quantity: " << invoice.getquantity() << endl; cout << "Price per item: $" << invoice.getpriceperitem() << endl; cout << "Invoice amount: $" << invoice.getinvoiceamount() << endl; // modify the invoice data members invoice.setpartnumber( "123456" ); invoice.setpartdescription( "Saw" ); invoice.setquantity( -5 ); // negative quantity, so quantity set to 0 invoice.setpriceperitem( 10 ); cout << "\ninvoice data members modified.\n\n"; // display the modified invoice data members and calculate new amount

7 cout << "Part number: " << invoice.getpartnumber() << endl; cout << "Part description: " << invoice.getpartdescription() << endl; cout << "Quantity: " << invoice.getquantity() << endl; cout << "Price per item: $" << invoice.getpriceperitem() << endl; cout << "Invoice amount: $" << invoice.getinvoiceamount() << endl; return 0; // indicate successful termination } // end main 3.14 // Exercise 3.14 Solution: Employee.h // Employee class definition. #include <string> // program uses C++ standard string class using std::string; // Employee class definition class Employee public: Employee( string, string, int ); // constructor sets data members void setfirstname( string ); // set first name string getfirstname(); // return first name void setlastname( string ); // set last name string getlastname(); // return last name void setmonthlysalary( int ); // set weekly salary int getmonthlysalary(); // return weekly salary private: string firstname; // Employee's first name string lastname; // Employee's last name int monthlysalary; // Employee's salary per month }; // end class Employee // Exercise 3.14 Solution: Employee.cpp // Employee class member-function definitions. #include "Employee.h" // Employee class definition // Employee constructor initializes the three data members Employee::Employee( string first, string last, int salary )

8 setfirstname( first ); // store first name setlastname( last ); // store last name setmonthlysalary( salary ); // validate and store monthly salary } // end Employee constructor // set first name void Employee::setFirstName( string name ) firstname = name; // no validation needed } // end function setfirstname // return first name string Employee::getFirstName() return firstname; } // end function getfirstname // set last name void Employee::setLastName( string name ) lastname = name; // no validation needed } // end function setlastname // return last name string Employee::getLastName() return lastname; } // end function getlastname // set monthly salary; if not positive, set to 0.0 void Employee::setMonthlySalary( int salary ) if ( salary > 0 ) // if salary is positive monthlysalary = salary; // set monthlysalary to salary if ( salary <= 0 ) // if salary is not positive monthlysalary = 0; // set monthlysalary to 0.0 } // end function setmonthlysalary // return monthly salary int Employee::getMonthlySalary() return monthlysalary;

9 } // end function getmonthlysalary // Exercise 3.14 Solution: ex03_14.cpp // Create and manipulate two Employee objects. #include "Employee.h" // include definition of class Employee // function main begins program execution int main() // create two Employee objects Employee employee1( "Lisa", "Roberts", 4500 ); Employee employee2( "Mark", "Stein", 4000 ); // display each Employee's yearly salary cout << "Employees' yearly salaries: " << endl; // retrieve and display employee1's monthly salary multiplied by 12 int monthlysalary1 = employee1.getmonthlysalary(); cout << employee1.getfirstname() << " " << employee1.getlastname() << ": $" << monthlysalary1 * 12 << endl; // retrieve and display employee2's monthly salary multiplied by 12 int monthlysalary2 = employee2.getmonthlysalary(); cout << employee2.getfirstname() << " " << employee2.getlastname() << ": $" << monthlysalary2 * 12 << endl; // give each Employee a 10% raise employee1.setmonthlysalary( monthlysalary1 + monthlysalary1 / 10 ); employee2.setmonthlysalary( monthlysalary2 + monthlysalary2 / 10 ); // display each Employee's yearly salary again cout << "\nemployees' yearly salaries after 10% raise: " << endl; // retrieve and display employee1's monthly salary multiplied by 12 monthlysalary1 = employee1.getmonthlysalary(); cout << employee1.getfirstname() << " " << employee1.getlastname() << ": $" << monthlysalary1 * 12 << endl; monthlysalary2 = employee2.getmonthlysalary(); cout << employee2.getfirstname() << " " << employee2.getlastname()

10 << ": $" << monthlysalary2 * 12 << endl; return 0; // indicate successful termination } // end main 3.15 // Exercise 3.15 Solution: Date.h // Definition of class Date. // class Date definition class Date public: Date( int, int, int ); // constructor initializes data members void setmonth( int ); // set month int getmonth(); // return month void setday( int ); // set day int getday(); // return day void setyear( int ); // set year int getyear(); // return year void displaydate(); // displays date in mm/dd/yyyy format private: int month; // the month of the date int day; // the day of the date int year; // the year of the date }; // end class Date // Exercise 3.15 Solution: Date.cpp // Member-function definitions for class Date. #include "Date.h" // include definition of class Date from Date.h // Date constructor that initializes the three data members; // assume values provided are correct (really should validate) Date::Date( int m, int d, int y ) setmonth( m ); setday( d ); setyear( y );

11 } // end Date constructor // set month void Date::setMonth( int m ) month = m; if ( month < 1 ) month = 1; if ( month > 12 ) month = 1; } // end function setmonth // return month int Date::getMonth() return month; } // end function getmonth // set day void Date::setDay( int d ) day = d; } // end function setday // return day int Date::getDay() return day; } // end function getday // set year void Date::setYear( int y ) year = y; } // end function setyear // return year int Date::getYear() return year; } // end function getyear

12 // print Date in the format mm/dd/yyyy void Date::displayDate() cout << month << '/' << day << '/' << year << endl; } // end function displaydate // Exercise 3.15 Solution: ex03_15.cpp // Demonstrates class Date's capabilities. #include "Date.h" // include definition of class Date from Date.h // function main begins program execution int main() Date date( 5, 6, 1981 ); // create a Date object for May 6, 1981 // display the values of the three Date data members cout << "Month: " << date.getmonth() << endl; cout << "Day: " << date.getday() << endl; cout << "Year: " << date.getyear() << endl; cout << "\noriginal date:" << endl; date.displaydate(); // output the Date as 5/6/1981 // modify the Date date.setmonth( 13 ); // invalid month date.setday( 1 ); date.setyear( 2005 ); cout << "\nnew date:" << endl; date.displaydate(); // output the modified date (1/1/2005) return 0; // indicate successful termination } // end main

13 第四章习题答案 4.27 // Exercise 4.27 Solution: Binary.h // Definition of class Binary. // Member function is defined in Binary.cpp // Binary class definition class Binary public: void converttodecimal(); // convert binary to decimal }; // end class Binary // Exercise 4.27 Solution: Binary.cpp // Member-function definitions for class Binary. using std::cin; #include "Binary.h" // include definition of class Binary // convert a binary number to a decimal number void Binary::convertToDecimal() int binary; // binary value int bit = 1; // bit positional value int decimal = 0; // decimal value // prompt for and read in a binary number cout << "Enter a binary number: "; cin >> binary; // convert to decimal equivalent while ( binary!= 0 ) decimal += binary % 10 * bit; binary /= 10; bit *= 2; } // end while loop

14 cout << "Decimal is: " << decimal << endl; } // end function converttodecimal // Exercise 4.27 Solution: ex04_27.cpp // Test program for class Binary. #include "Binary.h" // include definition of class Binary int main() Binary application; // create Binary object application.converttodecimal(); // function to convert to decimal return 0; // indicate successful termination } // end main 4.34 // Exercise 4.34 Part A Solution: Encrypt.cpp // Member-function definitions for class Encrypt. using std::cin; #include "Encrypt.h" // include definition of class Encrypt // encrypt a four-digit number void Encrypt::encrypt() int number; // original number int digit1; // first digit int digit2; // second digit int digit3; // third digit int digit4; // fourth digit int encryptednumber; // encrypted number // enter four-digit number to be encrypted cout << "Enter a four-digit number: "; cin >> number; // encrypt digit1 = ( number / ) % 10; digit2 = ( number % 1000 / ) % 10;

15 digit3 = ( number % 100 / ) % 10; digit4 = ( number % ) % 10; encryptednumber = digit1 * 10 + digit2 + digit3 * digit4 * 100; cout << "Encrypted number is " << encryptednumber << endl; } // end function encrypt // Exercise 4.34 Part B Solution: Decrypt.cpp // Member-function definitions for class Decrypt. using std::cin; #include "Decrypt.h" // include definition of class Decrypt // decrypt a number void Decrypt::decrypt() int number; // original number int digit1; // first digit int digit2; // second digit int digit3; // third digit int digit4; // fourth digit int decryptednumber; // encrypted number // enter an encrypted number to be decrypted cout << "Enter an encrypted number: "; cin >> number; // decrypt digit1 = ( number / ) % 10; digit2 = ( number % 1000 / ) % 10; digit3 = ( number % 100 / ) % 10; digit4 = ( number % ) % 10; decryptednumber = digit1 * 10 + digit2 + digit3 * digit4 * 100; cout << "Decrypted number is " << decryptednumber << endl; } // end function decrypt

16 4.35b // Exercise 4.35 Part B Solution: E.cpp // Member-function definitions for class E. using std::cin; #include "E.h" // include definition of class E from E.h // approximates the value of E void E::approximate() int number = 1; // counter int accuracy; // accuracy of estimate int factorial = 1; // value of factorial double e = 1.0; // estimate value of e // get accuracy cout << "Enter desired accuracy of e: "; cin >> accuracy; // calculate estimation while ( number < accuracy ) factorial *= number; e += 1.0 / factorial; number++; } // end while cout << "e is " << e << endl; } // end function approximate