Lecture5

C++programingforbeginners

9May2019

Lecturer:Dr.AnleWang&Dr.SergeySukhomlinov

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E-mail:anle.wang@uni-saarland.de

Lecture5

• Learnaboutarray;1-and2-dimensional• Explorehowtodeclareandmanipulatedataintoarrays;• Discoverhowtopassanarrayasparameterstoafunction;

• Afterthislecture,youshouldbeableto:- Defineandapply1Dand2Darraystocode.

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ContentsofLecture5

Lecture5

• Acollectionofafixednumberofcomponentswhereinallcomponentshavethesamedatatype;• Declarationruleisthesamewithvariables.• dataTypemeansthedatatypeofdatawhichstoresinthearray;• interExpisanindex,isanyexpressionwhosevalueisanonnegativeinteger;Mustbeconstantinteger!!!• []isthearraysubscriptingoperator;• Thearrayindexalwaysstartsfrom0.

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Whatisanarray?

Lecture5

• Callarraycomponents:- array[2]=12;- array[2]=array[4]+array[5];- doublevar1=array[8];

• Initializethe1Darray:- inta[10]={0,1,2,3,4,5,6,7,8,9};- inta[10]={0,1,2,3};- inta[5]={1,2,3,4,5};inta[]={1,2,3,4,5};

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Arraycomponents

0

10

12

3

5

7

8

6

2

array[0]array[1]

array[6]

array[5]array[4]

array[3]

array[2]

array[8]

array[7]

Lecture5

• Findthemaximumandminimumvalueofgivenintegerarray.• 14,17,25,3,65,4,9,0,12

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1Darrayprogramingexample

Lecture5

• Findthemaximumandminimumvalueofgivenintegerarray.• 14,17,25,3,65,4,9,0,12

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1Darrayprogramingexample

Lecture5

• Sortingdatainorderwithapplicationofarrays.- bubblesort;- selectsort;- insertsort;- quicksort;- mergesort;

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Sortingmethod(application)

step1 step2 step3 step4 step5

9 8 8 8 8

8 9 5 5 5

5 5 9 4 4

4 4 4 9 2

2 2 2 2 9

bubblesort

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Sortingmethod(application)

step1 step2 step3 step4 step5

9 8 8 8 8

8 9 5 5 5

5 5 9 4 4

4 4 4 9 2

2 2 2 2 9

bubblesort

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Sortingmethod(application)

selectsort

a[0] a[1] a[2] a[3] a[4]

3 6 1 9 4 step1

1 6 3 9 4 step2

1 3 6 9 4 step3

1 3 4 9 6 step4

1 3 4 6 9 step5

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Sortingmethod(application)

insertsort

a[0] a[1] a[2] a[3] a[4]

3 6 1 9 4 step1

1 3 6 9 4 step2

1 3 4 9 6 step3

1 3 4 6 9 step4

Lecture5

• Acollectionofafixednumberofcomponentswhereinallcomponentshavethesamedatatypeintwodimensions;• interExp1andinterExp2:numbersofrowandcolumninthematrices;

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Twodimensionalarray

[0] [1] [2]

[0]

[1]

[2]

[3]

num[2][1]

Lecture5

• Initializeallthecomponents:

• Initializepartialcomponents:

• Specialinitialization:

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Twodimensionalarray

Lecture5

• Rowprocessing:processaparticularrowofthearray.

• Columnprocessing:processaparticularcolumnofarray;

• Wholeprocessing:

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Twodimensionalarrayexample

Lecture5

• Findthemaximumofamatrixandoutputthevalueandrowandcolumn;• a[3][4]={{5,12,23,56},{19,28,36,46},{31,9,24,6}};

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Twodimensionalarrayexample

• Thecomponentsofarrayasaparameterofafunction.

Arrayasparametersinfunction

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• Thewholearraypassedasparameterstofunction.- Arrayarepassedbyreferenceonly;- Symbol&notusedwhendeclaringanarrayasaformalparameter;- Omitthesizeofarray.- Donotallowthefunctiontoreturnavalueofthetypearray.

Arrayasparametersinfunction

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• Sortingthenumberswithfollowingalgorithm

• Useafunctionselect_sort(intarray[],intn);Herenisthenumberofcomponents.

Arrayasparametersinfunction(example)

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a[0] a[1] a[2] a[3] a[4]

3 6 1 9 4

1 6 3 9 4

1 3 6 9 4

1 3 4 9 6

1 3 4 6 9

Arrayasparametersinfunction(example)

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• Ifweconsideratwo-dimensionalarray?

Arrayasparametersinfunction(2Darray)

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• Thebaseaddressofanarrayistheaddress,ormemorylocationofthefirstarraycomponent.• Ifarray[10]isa1-dimensionalarray,thebaseaddressistheaddressofarray[0].• Whenpassanarrayasaparameter,thebaseaddressoftheactualarrayispassedtotheformaladdress.

Arrayasparametersinfunction

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• Inputa2Dmatrix,andtrytoaveragetheelementsofeverycolumnandeveryrow.• Dumpoutthefollowingfigure(10rows):11112113311464115101051…

Exerciseofarrayapplication

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Exerciseofarrayapplication

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Exerciseofarrayapplication

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• Array:structureddatatypewithafixednumberofcomponentswithsamedatatype;• Declarationofarrayandhowtocallacomponentofarray;• Passarrayasparametertofunctions:onlybyreference;• Apairofindextoaccessanelementin2Darray;

Summaryofthislecture

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• Basicprogramwriting(realcode,pseudocode).• Understandingwhatthecodedoes?• Findthebugsinthecode.• Algorithmdesignandimplement.

• Nextweek(16/05)or23/05?

NextLecture(midTerm)

�25Lecture59May2019

• Pseudocodeisanarkficialandinformallanguagethathelpsprogrammersdevelopalgorithms.Pseudocodeisa"text-based"detail(algorithmic)designtool.

Pseudocode

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