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"<<
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