C++大學(xué)教程課后習(xí)題答案2

Chapter2

C++Basics

1.SolutionstotheProgrammingProjects:

1,Metric-EnglishunitsConversion

Ametrictonis35,273.92ounces.WriteaC++programtoreadtheweightofaboxofcereal

inouncesthenoutputthisweightinmetrictons,alongwiththenumberofboxestoyielda

metrictonofcereal.

Design:Toconvert14ounces(ofcereal)tometrictons,weusethe'ratioofunits*totellus

whethertodivideormultiply:

1metrictons

14ounces*--------*------------=0.000397metrictons

35,273ounces

Theuseofunitswillsimplifythedeterminationofwhethertodivideortomultiplyinmaking

aconversion.Noticethatounces/ouncebecomesunit-less,sothatweareleftwithmetricton

units.Thenumberofounceswillbevery,verymuchlargerthanthenumberofmetrictons.It

isthenreasonabletodividethenumberofouncesbythenumberofouncesinametrictonto

getthenumberofmetrictons.

NowletmetricTonsPerBoxbetheweightofthecerealboxinmetrictons.LetouncesPerBox

thebetheweightofthecerealboxinounces.TheninC++theformulabecomes:

constdoubleouncesPerMetric_ton=35272.92;

metricTonsPerBox=ouncesPerBox/ouncesPerMetricTon;

1

Copyright?2008PearsonEducation,Inc.PublishingasPearsonAddison-Wesley

ThisismetrictonsPERBOX,whencethenumberofBOX(es)PERmetrictonshouldbethe

reciprocal:

boxesPerMetricTon=1/metricTonsPerBox;

Oncethisanalysisismade,thecodeproceedsquickly:

//Purpose:Toconvertcerealboxweightfromouncesto

//metrictonstocomputenumberofboxestomakeupa

//metrictonofcereal.

?include<iostream>

usingnamespacestd;

ConstdoubleouncesPerMetricTon=35272.92;

intmain()

{

doubleouncesPerBox,metricTonsPerbox,

boxesPerMetricTon;

charans=*y1;

while('v'==ans||1Yf==ans)

(

cout<<''entertheweightinouncesofyour”

<<''favoritecereal:"<<endl;

cin>>ouncesPerBox;

metricTonsPerbox=

ouncesPerBox/ouncesPerMetricTon;

boxesPerMetricTon=1/metricTonsPerbox;

cout<<"metrictonsperbox="

<<metricTonsPerbox<<endl;

cout<<"boxestoyieldametricton="

<<boxesPerMetricTon<<endl;

cout<<”Yorycontinues,anyothercharacter”

<<''terminates."<<endl;

cin>>ans;

)

returno；

)

Asamplerunfollows:

entertheweightinouncesofyourfavoritecereal:

14

metrictonsperbox=0.000396905

boxestoyieldametricton=2519.49

Yorycontinues,anyothercharactersterminates.

y

entertheweightinouncesofyourfavoritecereal:

20

metrictonsperbox=0.000567007

boxestoyieldametricton=1763.65

Yorycontinues,anyothercharactersterminates.

n

2.LethalDose

Certainartificialsweetenersarepoisonousatsomedosagelevel.Itisdesiredtoknowhow

muchsodaadietercandrinkwithoutdying.Theproblemstatementgivesnoinformation

abouthowtoscaletheamountoftoxicityfromthedimensionsoftheexperimentalmouseto

thedimensionsofthedieter.Hencethestudentmustsupplythisnecessaryassumptionasbasis

forthecalculation.

Thissolutionsupposesthelethaldoseisdirectlyproportionaltotheweightofthesubject,

hence

weightOfDieter

lethalDoseDieter=lethalDoseMouse*----------------

weightOfMouse

Thisprogramacceptsweightofalethaldoseforamouse,theweightofthemouse,andthe

weightofthedieter,andcalculatestheamountofsweetenerthatwilljustkillthedieter,based

onthelethaldoseforamouseinthelab.Ifthestudenthasproblemswithgramsandpounds,a

poundis454grams.

Itisinterestingthattheresultprobablywantedisasafenumberofcans,whileallthedatacan

provideistheminimumlethalnumber!Somestudentswillprobablyrealizethis,butmy

experienceisthatmostwillnot.Ijustweighedacanofdietpopandsubtractedtheweightof

anemptycan.Theresultisabout35()grams.Thelabelclaims355ml,whichweighsvery

nearly355grams.Togetthelethalnumberofcansfromthenumberofgramsofsweetener,

youneedthenumberofgramsofsweetenerinacanofpop,andtheconcentrationof

sweetener,whichtheproblemassumes().1%,thatisaconversionfactorof0.001.

gramsSweetenerPerCan=350*0.001=0.35grams/can

cans=lethalDoseDieter/(0.35grams/can)

//Ch2Prob5.cc

//Input:lethaldoseofsweetenerforalabmouse,weights

//ofmouseanddieterAandconcentrationofsweetenerina

//soda.

//Output:lethaldoseofsodainnumberofcans.

//Assumption:lethaldoseproportionaltoweightofsubject

//Concentrationofsweetenerinthesodais1/10percent

?include<iostream>

usingnamespacestd;

constdoubleconcentration=.001;//1/10of1percent

constdoublecanWeight=350;

constdoublegramsSweetnerPerCan=canWeight*concentration;

//unitsofgrams/can

intmain()

(

double1ethalDoseMouse,lethalDoseDieterf

weightMousezweightDieter;//units:grams

doublecans;

charans;

do

(

cout<<"EntertheweightofthemouseingramsH

<<endl;

cin>>weightMouse;

cout<<"Enterthelethaldoseforthemousein''

<<"grams”<<endl;

cin>>lethalDoseMouse;

cout<<"Enterthedesiredweightofthedieterin”

<<''grams”<<endl;

cin>>weightDieter;

lethalDoseDieter=

lethalDoseMouse*weightDieter/weightMouse;

cout<<"Fortheseparameters:\nmouseweight:

<<weightMouse

<<"grams”<<endl

<<Hlethaldoseforthemouse:“

<<lethalDoseMouse

<<"grams"<<endl

<<"Dieterweight:“<<weightDieter

<<”grams”<<endl

<<nThelethaldoseingramsofsweeteneris:"

<<lethalDoseDieter<<endl;

cans=lethalDoseDieter/gramsSweetnerPerCan;

cout<<"Lethalnumberofcansofpop:"

<<cans<<endl;

cout<<nYorycontinues,anyothercharacterquits

<<endl;

cin>>ans;

}while(1y*==ans||*Y*==ans);

returno；

)

Atypicalrunfollows:

17:23:09:-/AW$a.out

Entertheweightofthemouseingrams

15

Enterthelethaldoseforthemouseingrams

100

Enterthedesiredweightofthedieter,ingrams

45400

Fortheseparameters:

mouseweight:15grams

lethaldoseforthemouse:100grams

Dieterweight:45400grams

Thelethaldoseingramsofsweeteneris:302667

Lethalnumberofcansofpop:864762

Yorycontinues,anyothercharacterquits

y

Entertheweightofthemouseingrams

30

Enterthelethaldoseforthemouseingrams

100

Enterthedesiredweightofthedieter,ingrams

45400

Fortheseparameters:

mouseweight:30grams

lethaldoseforthemouse:100grams

Dieterweight:45400grams

Thelethaldoseingramsofsweeteneris:151333

Lethalnumberofcansofpop:432381

Yorycontinues,anyothercharacterquits

q

17:23:56:?/AW$

3.PayIncrease

Theworkershavewona7.6%payincrease,effective6monthsretroactively.Thisprogramis

toacceptthepreviousannualsalary,thenoutputstheretroactivepayduetheemployee,the

newannualsalary,andthenewmonthlysalary.Allowusertorepeatasdesired.The

appropriateformulaeare:

constdoubleINCREASE0.076;

newSalary=salary*(1+INCREASE);

monthly=salary/12;

retroactive=(salary-oldSalary)/2;

Thecodefollows:

//Ch2Prob3.cc

//Given6mosretroactive7.6%payincrease,

//inputsalary

//Outputnewannualandmonthlysalaries,retroactivepay

?include<iostream>

usingnamespacestd;

constdoubleINCREASE=0.076;

intmain()

(

doubleoldSalaryzsalaryfmonthly,retroactive;

charans;

cout<<"Entercurrentannualsalary.H<<endl

<<HI*11returnnewannualsalary,monthly〃

<<''salary,andretroactivepay.”<<endl;

cin>>oldSalary;//oldannualsalary

salary=oldSalary*(1+INCREASE);//newannualsalary

monthly=salary/12;

retroactive=(salary-oldSalary)/2;

cout<<"newannualsalary”<<salary<<endl;

cout<<"newmonthlysalary”<<monthly<<endl;

cout<<"retroactivesalarydue:"

<<retroactive<<endl;

return0;

)

17:50:12:-/AW$a.out

Entercurrentannualsalary.

100000

I*11returnnewannualsalary,monthlysalary,and

retroactivepay.

newannualsalary107600

newmonthlysalary8966.67

retroactivesalarydue:3800

4.RetroactiveSalary

//File:Ch2.4.cpp

//ModifyprogramfromProblem#3sothatitcalculates

retroactive

//salaryforaworkerforanumberofmonthsenteredbythe

user?

//Givena7.6%payincrease,

//inputsalary

//inputnumberofmonthstocomputeretroactivesalary

//Outputnewannualandmonthlysalaries,retroactivepay

#include<iostream>

constdoubleINCREASE=0.076;

intmain()

(

usingstd::cout;

usingstd::cin;

usingstd::endl;

doubleoldSalaryzsalary,monthly,oldMonthlyzretroactive;

intnumberOfMonths;//numberofmonthstopayretroactive

increase

charans;

cout<<HEntercurrentannualsalaryandanumberofmonths\n

<<"forwhichyouwishtocomputeretroactivepay.\n"

<<"1,11returnnewannualsalary,monthly”

<<"salary,andretroactivepay.n<<endl;

cin>>oldSalary;//oldannualsalary

cin>>numberOfMonths;

salary=oldSalary*(1+工NCREASE);//newannualsalary

oldMonthly=oldSalary/12;

monthly=salary/12;

retroactive=(monthly-oldMonthly)*numberOfMonths;

//retroactive=(salary-oldSalary)/2;//sixmonths

retroactivepayincrease.

cout<<Hnewannualsalary”<<salary<<endl;

cout<<Hnewmonthlysalary”<<monthly<<endl;

cout<<"retroactivesalarydue:"

<<retroactive<<endl;

return0;

)

/*

Typicalrun

Entercurrentannualsalaryandanumberofmonths

forwhichyouwishtocomputeretroactivepay.

If11returnnewannualsalary,monthlysalary,andretroactive

pay.

12000

9

newannualsalary12912

newmonthlysalary1076

retroactivesalarydue:684

Pressanykeytocontinue

*/

5.Nosolutionprovided.

6.Nosolutionprovided.

7.Payroll

Thisprobleminvolvespayrollandusestheselectionconstruct.Apossiblerestatement:An

hourlyemployee'sregularpayRateis$16.78/hourforhoursWorked<=40hours.

IfhoursWorked>40hours,then(hoursWorked-40)ispaidatanovertime

premiumrateof1.5*payRate.FICA(socialsecurity)taxis6%andFederalincome

taxis14%.Unionduesof$10/weekarewithheld.Ifthereare3ormorecovered

dependents,$15moreiswithheldfordependenthealthinsurance.

a)Writeaprogramthat,onaweeklybasis,acceptshoursworkedthenoutputsgrosspay,each

withholdingamount,andnet(take-home)pay.

b)AddYepeatatuserdiscretion1feature.

IwasunpleasantlysurprisedtofindthatwithearlyGNUg++,youcannotusealeading0

(suchasanSSN034567891)inasequenceofintegerinputs.Thegnuiostreamslibrarytook

theintegertobezeroandwentdirectlytothenextinput!Youeitherhavetoeitherusean

arrayofchar,or9charvariablestoavoidthisrestriction.

Otherwise,thecodeisfairlystraightforward.

//fileCh2Prob7.cc

//payrollproblem:

//Inputs:hoursWorked^numberofdependents

//Outputs:grosspayreachdeduction,netpay

//

//Thisisthe1repeatatuserdiscretion1version

//Outline:

//Inarealpayrollprogram,eachofthesevalueswouldbe

//storedinafileafterthepayrollcalculationwasprinted

//toareport.

//

//regularpayRate=$10.78/hourforhoursWorked<=40

//hours.

//IfhoursWorked>40hours,

//overtimePay=(hoursWorked-40)*1.5*PAY_RATE.

//FICA(socialsecurity)taxrateis6%

//Federalincometaxrateis14%.

//Uniondues=$10/week.

//Ifnumberofdependents>=3

//$15moreiswithheldfordependenthealthinsurance.

//

?include<iostream>

usingnamespacestd;

constdoublePAY_RATE=16.78；

constdoubleSS_TAX_RATE=0.06；

constdoubleFed工RS_RATE=0.14;

constdoubleSTATE_TAX_RATE=o.05；

constdoubleUNION_DUES=10.o；

constdoubleOVERTIME_FACTOR=1.5；

constdoubleHEALTH_INSURANCE=15.o；

intmain()

(

doublehoursWorked,grossPay,overTime,fica,

incomeTax,stateTax,union_dues,netPay;

intnumberDependents,employeeNumber;

charans;

//settheoutputtotwoplaces,andforce.00forcents

cout.setf(ios::showpoint);

cout.setf(ios::fixed);

cout.precision(2);

//computepayroll

do

(

cout<<"EnteremployeeSSN(digitsonly,“

<<''nospacesordashes)\nz,;

cin>>employeeNumber;

cout<<''Pleasetheenterhoursworkedandnumber''

<<''ofemployees.<<endl;

cin>>hoursWorked;

cin>>numberDependents;

cout<<endl;

if(hoursWorked<=40)

grossPay=hoursWorked*PAY__RATE;

else

{

overTime=

(hoursWorked-40)*PAY_RATE*OVERTIME_FACTOR;

grossPay=40*PAY_RATE+overTime;

)

fica=grossPay*SS_TAX_RATE;

incomeTax=grossPay*FedIRS_RATE;

stateTax=grossPay*STATE_TAX_RATE;

netPay=

grossPay-fica-incomeTax

-UN工ON_DUES-stateTax;

if(numberDependents>=3)

netPay=netPay-HEALTH.INSURANCE;

//nowprintreportforthisemployee:

cout<<"Employeenumber:“

<<employeeNumber<<endl;

cout<<"hoursworked:“<<hoursWorked<<endl;

cout<<"regularpayrate:"<<PAY_RATE<<endl;

if(hoursWorked>40)

(

cout<<"overtimehoursworked:“

<<hoursWorked-40<<endl;

cout<<"withovertimepremium:"

<<OVERT工ME_FACTOR<<endl;

)

cout<<"grosspay:"<<grossPay<<endl;

cout<<HFICAtaxwithheld:“<<fica<<endl;

cout<<"FederalIncomeTaxwithheld:“

<<incomeTax<<endl;

cout<<"StateTaxwithheld:“<<stateTax<<endl;

if(numberDependents>=3)

cout<<"HealthInsurancePremiumwithheld:"

<<HEALTH.INSURANCE<<endl;

cout<<HFlabbergaster*sUnionDueswithheld:

<<UN工ON_DUES<<endl;

cout<<"NetPay:"<<netPay<<endl<<endl;

cout<<"Computepayforanotheremployee?”

<<''Y/yrepeats,anyotherendsH<<endl;

cin>>ans;

}while('v'==ans||1Y1==ans);

return0；

)

//Atypicalrun:

14:26:48:~/AW$a.out

EnteremployeeSSN(digitsonly,nospacesordashes)

234567890

Pleasetheenterhoursworkedandnumberofemployees.

10

1

Employeenumber:234567890

hoursworked:10.00

regularpayrate:16.78

grosspay:167.80

FICAtaxwithheld:10.07

FederalIncomeTaxwithheld:23.49

StateTaxwithheld:8.39

Flabbergaster1sUnionDueswithheld:10.00

NetPay:115.85

Computepayforanotheremployee?Y/yrepeats,anyotherends

y

EnteremployeeSSN(digitsonly,nospacesordashes)

987654321

Pleasetheenterhoursworkedandnumberofemployees.

10

3

Employeenumber:987654321

hoursworked:10.00

regularpayrate:16.78

grosspay:167.80

FICAtaxwithheld:10.07

FederalIncomeTaxwithheld:23.49

StateTaxwithheld:8.39

HealthInsurancePremiumwithheld:35.00

Flabbergaster1sUnionDueswithheld:10.00

NetPay:80.85

Computepayforanotheremployee?Y/yrepeats,anyotherends

y

EnteremployeeSSN(digitsonly,nospacesordashes)

123456789

Pleasetheenterhoursworkedandnumberofemployees.

45

3

Employeenumber:123456789

hoursworked:45.00

regularpayrate:16.78

overtimehoursworked:5.00

withovertimepremium:1.50

grosspay:797.05

FICAtaxwithheld:47.82

FederalIncomeTaxwithheld:111.59

StateTaxwithheld:39.85

HealthInsurancePremiumwithheld:35.00

Flabbergaster*sUnionDueswithheld:10.00

NetPay:552.79

Computepayforanotheremployee?Y/yrepeats,anyotherends

n

14:28:12:?/AW$

8.Nosolutionprovided.

9.InstallmentLoanTime

Nodownpayment,18percent/year,paymentof$50/month,paymentgoesfirsttointerest,

balancetoprincipal.Writeaprogramthatdeterminesthenumberofmonthsitwilltaketopay

offa$1000stereo.Thefollowingcodealsooutputsthemonthlystatusoftheloan,

?include<iostream>

usingnamespacestd;

//chapter2problem9.

intmain()

(

doubleprincipal=1000.;

doubleinterestArate=0.015;

intmonths=0;

cout<<nmonths\tinterest\tprincipa1H<<endl;

while(principal>0)

(

months++;

interest=principal*rate;

principal=principal-(50-interest);

if(principal>0)

cout<<months<<n\t"<<interest<<n\t\t

<<principal<<endl;

)

cout<<"numberofpayments="<<months;

//undotheinterationthatdroveprincipalnegative:

principal=principal+(50-interest);

//includeinterestforlastmonth:

interest=principal*0.015;

principal=principal+interest;

cout<<”lastmonthsinterest="<<interest;

cout<<”lastpayment="<<principal<<endl;

return0;

)

Testingisomittedforthisproblem.

10.Nosolutionprovided.

11.Separatenumbersbysign,computesumsandaverages

//ProgrammingProblem11

//Readtenintvaluesoutput

//sumandaverageofpositivenumbers

//sumandaverageofnonpositivenumbers,

//sumandaverageofallnumbers,

//

//Averagesareusuallyfloatingpointnumbers.Wemulitply

//thenumeratoroftheaveragecomputationby1.0tomake

//theintvaluesconvertautomaticallytodouble.

#include<iostream>

intmain()

(

usingstd::cout;

usingstd::cin;

usingstd::endl;

intvalue,sum=0,sumPos=0,sumNonPos=0;

intcountPos=0,countNeg=0;

cout<<"Entertennumbers,I*11echoyournumberandcompute\nn

<<"thesumandaverageofpositivenumbers\nn

<<"thesumandaverageofnonpositivenumbers\nn

<<"thesumandaverageofallnumbers\n\nM;

for(inti=0;i<10;i++)

(

cin>>value;

cout<<"value"<<value<<endl;

sum+=value;

if(value>0)

(

sumPos+=value;

countPos++;

)

else

(

sumNonPos+=value;

countNeg++;

)

)

cout<<"SumofPositivenumbersis”

<<sumPos<<endl;

cout<<"AverageofPositivenumbersis”

<<(1.0*sumPos)/countPos<<endl;

cout<<"SumofNonPositivenumbersis

<<sumNonPos<<endl;

cout<<nAverageofNonPositivenumbersis”

<<(1.0*sumNonPos)/countNeg<<endl;

cout<<"Sum"<<sum<<endl;

cout<<nAverageis”<<(1.0*sum)/(countPos+countNeg)<<endl;

if((countPos+countNeg)!=10)

cout<<"Countnot10,errorsomeplace\nn;

return0;

)

/*

Typicalrun

Entertennumbers,I*11echoyournumberandcompute

thesumandaverageofpositivenumbers

thesumandaverageofnonpositivenumbers

thesumandaverageofallnumbers

4

value4

5

value5

-1

value-1

3

value3

-4

value-4

-3

value-3

9

value9

8

value8

7

value7

2

value2

SumofPositivenumbersis38

AverageofPositivenumbersis5.42857

SumofNonPositivenumbersis-8

AverageofNonPositivenumbersis-2.66667

Sum30

Averageis3

Pressanykeytocontinue

12.

//

***********************************************************************

//Ch2Projl2.cpp

//

//Thisprogramcomputesthesquarerootofanumbern

//usingtheBabylonianalgorithm.

//

***********************************************************************

#include<iostream>

usingnamespacestd;

//====================

//mainfunction

//====================

intmain()

doubleguess,previousguess,nzr;

//Inputnumbertocomputethesquarerootof

cout<<"Enternumbertocomputethesquarerootof.n<<endl;

cin>>n;

//Initialguess

previousguess=n;

guess=n/2;

//Repeatuntilguessiswithin1%ofthepreviousguess

while(((previousguess-guess)/previousguess)>0.01)

(

previousguess=guess;

r=n/guess;

guess=(guess+r)/2;

)

cout<<"Theestimateofthesquarerootof"<<n<<"is"

<<guess<<endl;

return0;

}

13.

//

*********************************************************************

//Ch2Proj13.cpp

//

//ThisprograminputsaspeedinMPHandconvertsitto

//MinutesandSecondspermile,asmightbeoutputonatreadmill.

//

*********************************************************************

#include<iostream>

usingnamespacestd;

//====================

//mainfunction

//====================

intmain()

(

doublemilesPerHour,hoursPerMile,minutesPerMile,secondsPace;

intminutesPace;

//Inputmilesperhour

cout<<"Enterspeedinmilesperhour:n<<endl;

cin>>milesPerHour;

//Computeinverse,whichishourspermile

hoursPerMile=1.0/milesPerHour;

//Converttominutespermilewhichis60seconds/hour*hoursPerMile

minutesPerMile=60*hoursPerMile;

//Extractminutesbyconvertingtoaninteger,while

//truncatesanyvalueafterthedecimalpoint

minutesPace=static_cast<int>(minutesPerMile);

//Secondsistheremainingnumberofminutes*60

secondsPace=(minutesPerMile-minutesPace)*60;

cout<<milesPerHour<<”milesperhourisapaceof”<<

minutesPace<<”minutesand”<<secondsPace<<"seconds."<<

endl;

return0;

}

14.

//

'A?**********************************************************************

//Ch2Proj14.cpp

//

//Thisprogramplaysasimplegameof"MadLibs".

//

***********************************************************************

#include<iostream>

usingnamespacestd;

//====================

//mainfunction

//====================

intmain()

(

stringinstructorName;

stringyourName;

stringfood;

intnum;

stringadjective;

stringcolor;

stringanimal;

cout<<"WelcometoMadLibs!Enteryourname:"<<endl;

cin>>yourName;

cout<<"Enteryourinstructor1sfirstorlastname.n<<endl;

cin>>instructorName;

cout<<"Enterafood.”<<endl;

cin>>food;

cout<<"Enteranumberbetween100and120."<<endl;

cin>>num;

cout<<"Enteranadjective.n<<endl;

cin>>adjective;

cout<<"Enteracolor.n<<endl;

cin>>color;

cout<<"Enterananimal.H<<endl;

cin>>animal;

cout<<endl;

cout<<"DearInstructor”<<instructorName<<<<endl;

cout<<endl;

cout<<"工amsorrythatIamunabletoturninmyhomeworkatthis

time.”

<<endl;

cout<<"First,Iatearotten'*<<food<<”whichmademeturn*'<<

color<<"and"<<endl;

cout<<"extremelyill.Icamedownwithafeverof”<<num<<

<<endl;

cout<<"Next,my"<<adjective<<”pet”<<animal<<”musthave

<<

"smelledtheremains”<<endl;

cout