用C++解决问题第十版Chapter 5 Functions for All Subtasks.docx

用C++解决问题第十版Chapter 5 Functions for All Subtasks.docx

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用C++解决问题第十版Chapter5FunctionsforAllSubtasks

Chapter5

FunctionsforAllSubtasks

1.SolutionstoSelectedPracticeProgramsandProgrammingProjects

Detailedsolutionsselectedprojectsarepresentedhere.Therestareessentiallythesameproblems,exceptforwhatisbeingconverted.Notesabouttheremainingproblemsareincluded.

Oneofthemoreimportantthingsinprogrammingisplanning,evenforthesimplestprogram.Iftheplanningisthorough,thecodingwillbeeasy,andtheonlyerrorslikelytobeencounteredaresyntaxerrors,usuallycausedbyeithertypingerrors,aboundaryconditionproblem（frequently,anoffbyoneerror）,or（wehopenot）lackofknowledgeofthelanguagedetails.

PracticeProgram1:

Statistics

Computeaverageandstandarddeviationof4entries.

GeneralremarksareinthecodefilewhichIpresenthere:

#include

usingnamespacestd;

/*

Task:

Writeafunctionthatcomputesaverage（Iwillcallthisthearithmeticmeanorsimplythemean）andstandarddeviationoffourscores.Theaverageormean,avg,iscomputedas

avg=（s1+s2+s3+s4）/4

Thestandarddeviationiscomputedas

wherea=avg.Notethatsomestatisticiansmaywishtouse3insteadof4.Wewilluse4.

Input:

scoress1s2s3s4

Output:

standarddeviationandmean.

Required:

Thefunctionistohave6parameters.Thisfunctioncallstwoothersthatcomputethemeanandthestddeviation.Adriverwithaloopshouldbewrittentotestthefunctionattheuser'soption.

*/

//functiondeclaration（orprototype）

//Whenused,themathlibrarymustbelinkedtothe//executable.

#include//forsqrt

usingnamespacestd;

voidaverage（doubles1,doubles2,doubles3,

doubles4,double&avg）

{

avg=（s1+s2+s3+s4）/4;

}

//Preconditions:

averagefunctionmusthavebeencalledon

//thedata,andthevalueoftheaveragepassedintothe//parametera

//Postconditions:

Standarddeviationispassedbackin

//thevariablestdDev

voidsD（doubles1,doubles2,doubles3,doubles4,

doublea,double&stdDev）

{

stdDev=sqrt（（s1-a）*（s1-a）+（s2-a）*（s2-a）

+（s3-a）*（s3-a）+（s4-a）*（s4-a））/4;

}

voidstatistics（doubles1,doubles2,doubles3,doubles4,

double&avg,double&stdDev）;

//Preconditions:

thisfunctioniscalledwithanysetof

//values.Verylargeorverysmallnumbersaresubjectto

//errorsinthecalculation.Analysisofthissortoferror//isbeyondthescopeofthischapter.

//PostConditions:

avgissettothemeanofs1,s2,s3,s4

//andstdDevissettothestandarddeviationofs1..s4

//functiondefinition:

voidstatistics（doubles1,doubles2,doubles3,doubles4,

double&avg,double&stdDev）

{

average（s1,s2,s3,s4,avg）;

sD（s1,s2,s3,s4,avg,stdDev）;

}

intmain（）

{

doubles1,s2,s3,s4,avg,stdDev;

charans;

do

{

cout<<"Enter4decimalnumbers,"

<<"Iwillgiveyouthemean"

<

<<"andstandarddeviationofthedata"<

cin>>s1>>s2>>s3>>s4;

statistics（s1,s2,s3,s4,avg,stdDev）;

cout<<"meanof"<

<<""<

<<"thestandarddeviationof"

<<"thesenumbersis"<

cout<<"yorYcontinues,anyotherterminates"<

cin>>ans;

}while（'Y'==ans||'y'==ans）;

return0;

}

Atypicalrunfollows:

21:

44:

35:

~/AW$a.out

Enter4decimalnumbers,Iwillgiveyouthemean

andstandarddeviationofthedata

12.313.410.59.0

meanof12.313.410.59is11.3

thestandarddeviationofthesenumbersis0.841873

yorYcontinues,anyotherterminates

y

Enter4decimalnumbers,Iwillgiveyouthemean

andstandarddeviationofthedata

1234

meanof1234is2.5

thestandarddeviationofthesenumbersis0.559017

yorYcontinues,anyotherterminates

n

21:

45:

05:

~/AW$

PracticeProgram2:

ConvertFeet/InchestoMeters

Conversionoffeet/inchestometers:

//Task:

Convertfeet/inchestometers

//Input:

alengthinfeetandinches,withpossibledecimal

//partofinches

//Output:

alengthinmeters,with2decimalplaces,which

//arethe'centimeters'specifiedintheproblem.

//Required:

functionsforinput,computation,andoutput.

//Includealooptorepeatthecalculationattheuser's

//option.Remarks:

Thecomputationisasimpleconversionfrom

//feet+inchestofeetwithadecimalpart,thentometers.

//Outputisrestrictedto2decimalplaces.

//

//By'metersandcentimeters'theauthormeansthatthe

//outputistobemeterswithtwodecimalplaces-whichis

//metersandcentimeters.Imentionthisbecausemystudents

//alwaysstumbleatthisbecauseofalackofknowledgeof

//themetricsystem.

#include

usingnamespacestd;

voidinput（int&feet,double&inches）;

//Precondition:

functioniscalled

//Postcondition:

//PromptgiventotheuserforinputintheformatFFII,

//whereFFisintegernumberoffeetandIIisadouble

//numberofinches.feetandinchesarereturnedasentered

//bytheuser.

voidconvert（intfeet,doubleinches,double&meters）;

//Preconditions:

//REQUIREDCONSTANTS:

INCHES_PER_FOOT,METERS_PER_FOOT

//inches<12,feetwithinrangeofvaluesforinttype

//Postconditions:

//metersassigned0.3048*（feet+inches/12）

//observethatthecentimeterrequirementismetby

//thevalueofthefirsttwodecimalplacesoftheconverted

//feet,inchesinput.

voidoutput（intfeet,doubleinches,doublemeters）;

//input:

theformalargumentformetersfitsintoadouble

//output:

//"thevalueoffeet,inches"

//"convertedtometers,centimetersis"

//wheremetersisdisplayedasanumberwithtwodecimal

//places

intmain（）

{

intfeet;

doubleinches,meters;

charans;

do

{

input（feet,inches）;

convert（feet,inches,meters）;

output（feet,inches,meters）;

cout<<"Yorycontinues,anyothercharacterquits"

<

cin>>ans;

}while（'Y'==ans||'y'==ans）;

return0;

}

voidinput（int&feet,double&inches）

{

cout<<"Enterfeetasaninteger:

"<

cin>>feet;

cout<<"Enterinchesasadouble:

"<

cin>>inches;

}

constdoubleMETERS_PER_FOOT=0.3048;

constdoubleINCHES_PER_FOOT=12.0;

voidconvert（intfeet,doubleinches,double&meters）

{

meters=METERS_PER_FOOT*（feet+inches/INCHES_PER_FOOT）;

}

voidoutput（intfeet,doubleinches,doublemeters）

{

//inches,metersdisplayedasanumberwithtwodecimal

//places

cout.setf（ios:

:

showpoint）;

cout.setf（ios:

:

fixed）;

cout.precision

（2）;

cout<<"thevalueoffeet,inches"<

<

<<"convertedtometers,centimetersis"

<

}

/*

Atypicalrunfollows:

06:

59:

16:

~/AW$a.out

Enterfeetasaninteger:

5

Enterinchesasadouble:

7

thevalueoffeet,inches5,7.00

convertedtometers,centimetersis1.70

Yorycontinues,anyothercharacterquits

y

Enterfeetasaninteger:

245

Enterinchesasadouble:

0

thevalueoffeet,inches245,0.00

convertedtometers,centimetersis74.68

Yorycontinues,anyothercharacterquits

q

06:

59:

49:

~/AW$

*/

PracticeProgram3:

ConversionmetrictoEnglish

Conversionofmetersbacktofeetandinches

//Task:

Convertmeterswithcentimeters（justthedecimal

//partofmeters）tofeet/inches

//

//Input:

alengthinfeetandinches,withpossibledecimal

//partofinches

//Output:

Alengthmeasuredinfeetwithanydecimalfraction

//convertedtoinchesbymultiplyingby12.Fractionsofan

//incharerepresentedby2decimalplaces.

//

//Required:

functionsforinput,computation,andoutput.

//Includealooptorepeatthecalculationattheuser's

//option.

//

//Remark:

Thecomputationisasimpleconversionfrommeters

//tofeet,inches,whereincheshasadecimalpart.

//Outputisrestrictedto2decimalplaces

//Comment:

PleaseseeProblem4fordiscussionof'metersand//centimeters'

#include

usingnamespacestd;

voidinput（double&meters）;

//Precondition:

functioniscalled

//Postcondition:

//Promptgiventotheuserforinputofanumberofmetersas

//adouble.inputofadoubleformetershasbeenaccepted

voidconvert（int&feet,double&inches,doublemeters）;

//Preconditions:

//REQUIREDCONSTANTS:

INCHES_PER_FOOT,METERS_PER_FOOT

//Postconditions:

//feetisassignedtheintegerpartofmeters（after

//conversiontofeetunits）inchesisassignedthe

//fractionalpartoffeet（afterconversiontoinchunits

voidoutput（intfeet,doubleinches,doublemeters）;

//input:

theformalargumentformetersfitsintoadouble

//output:

//"thevalueofmeters,centimetersis:

"

//"convertedtoEnglishmeasureis"

//"feet,""inches"

//wheremetersisdisplayedasanumberwithtwodecimal

//places

intmain（）

{

intfeet;

doubleinches,meters;

charans;

do

{

input（meters）;

convert（feet,inches,meters）;

output（feet,inches,meters）;

cout<<"Yorycontinues,anyothercharacterquits"

<

cin>>ans;

}while（'Y'==ans||'y'==ans）;

return0;

}

voidinput（double&meters）

{

cout<<"Enteranumberofmetersasadouble\n";

cin>>meters;

}

constdoubleMETERS_PER_FOOT=0.3048;

constdoubleINCHES_PER_FOOT=12.0;

voidconvert（int&feet,double&inches,doublemeters）

{

doubledfeet;

dfeet=meters/METERS_PER_FOOT;

feet=int（dfeet）;

inches=（dfeet-feet）*INCHES_PER_FOOT;

}

voidoutput（intfeet,doubleinches,doublemeters）

{

//metersisdisplayedasadoublewithtwodecimalplaces

//feetisdisplayedasint,inchesasdoublewithtwo

//decimalplaces

cout.setf（ios:

:

showpoint）;

cout.setf（ios:

:

fixed）;

cout.precision

（2）;

cout<<"Thevalueofmeters,centimeters"<

<