Chapter 07 Arrays

8/13/2019 Chapter 07 Arrays

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Copyright 2012 Pearson Education, Inc.Copyright 2012 Pearson Education, Inc.

Chapter 7:

Arrays


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7.1 Arrays Hold Multiple Values


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Arrays Hold Multiple Values

Array: variable that can store multiplevalues of the same type

Values are stored in adjacent memorylocations

Declared usin [] operator:

int tests[5];


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Array ! Memory "ayout

#he definition: int tests[5];

allocates the follo$in memory:

firstelement

secondelement

thirdelement

fourthelement

fifthelement


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Array #erminolo y

%n the definition int tests[5]; int is the data type of the array elements

tests is the name of the array 5, in [5], is the si&e declarator. %t sho$s

the number of elements in the array.

#he si&e of an array is 'number ofelements( ) 'si&e of each element(


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Array #erminolo y

#he si&e of an array is: * the total number of bytes allocated for it

* 'number of elements( ) 'number of bytes foreach element(

+,amples:

int tests[5] is an array of - bytes/

assumin 0 bytes for an intlong double measures[10] is an array of bytes/ assumin bytes for a long double


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2i&e Declarators

3amed constants are commonly used assi&e declarators.

const int SIZE = 5;int tests[SIZE];

#his eases pro ram maintenance $henthe si&e of the array needs to be chan ed.



7.- Accessin Array +lements



Accessin Array +lements

+ach element in an array is assi ned auni4ue subscript .

2ubscripts start at

0 1 2 3

subscripts

:




#he last element5s subscript is n!1 $here n is the number of elements in the array.

0 1 2 3subscripts:




Array elements can be used as re ular variables:

tests[0] = !";cout ## tests[0];cin $$ tests[1];tests[ ] = tests[0] % tests[1];

Arrays must be accessed via individualelements:cout ## tests; && not legal



(Program Continues)



Here are the contents of the 'ours array/ $ith the values

entered by the user in the e,ample output:



Accessin Array 6ontents

6an access element $ith a constant orliteral subscript:

cout ## tests[3] ## endl;

6an use inte er e,pression as subscript:

int i = 5;cout ## tests[i] ## endl;



sin a "oop to 2tep #hrou han Array +,ample * #he follo$in code defines an

array/ numbers / and assi ns 88 to eachelement:

const int ())(*+SIZE = 5;int numbers[())(*+SIZE];

or -int count = 0; count # ())(*+SIZE; count%%. numbers[count] = "";


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A 6loser "oo9 At the "oop


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Default %nitiali&ation

lobal array all elements initiali&ed to 0 by default

"ocal array all elements uninitialized bydefault


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7.;3o


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3o hen you use a value as an arraysubscript/ 6== does not chec9 it to ma9e

sure it is a valid subscript.

%n other $ords/ you can use subscripts

that are beyond the bounds of the array.


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6ode ?rom @ro ram 7!

#he follo$in code defines a three!element array/ and then $rites five valuesto itB


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>hat the 6ode Does


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3o


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Cff!


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Array Initialization7.0


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7.0 Array %nitiali&ation


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Array %nitiali&ation

Arrays can be initiali&ed $ith aninitiali&ation list:

const int SIZE = 5;int tests[SIZE] = !",42,"1,!!,4 ;

#he values are stored in the array in theorder in $hich they appear in the list.

#he initiali&ation list cannot e,ceed thearray si&e.

7!-


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6ode ?rom @ro ram 7!


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@artial Array %nitiali&ation

%f array is initiali&ed $ith fe$er initialvalues than the si&e declarator/ theremainin elements $ill be set to 06


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%mplicit Array 2i&in

6an determine array si&e by the si&e ofthe initiali&ation list:

int 7ui88es[]= 12,1!,15,11 ;

Must use either array si&e declarator orinitiali&ation list at array definition

12 1! 15 11


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7.@rocessin Array 6ontents


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@rocessin Array 6ontents

Array elements can be treated as ordinaryvariables of the same type as the array

>hen usin %%/ operators/ don5tconfuse the element $ith the subscript:

tests[i]%%; && add 1 to tests[i]

tests[i%%]; && increment i, no && e ect on tests


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Array Assi nment

#o copy one array to another/ Don5t try to assi n one array to the other:

ne9/ests = tests; && :on t 9or;else cout ## >/'e arra s are not e7ual Gn>;


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7.sin @arallel Arrays


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sin @arallel Arrays

@arallel arrays: t$o or more arrays thatcontain related data

A subscript is used to relate arrays:elements at same subscript are related

Arrays may be of different types


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@arallel Array +,ample

const int SIZE = 5; && (rra si8eint id[SIZE]; && student IHdouble a@erage[SIZE]; && course a@eragec'ar grade[SIZE]; && course grade

or-int i = 0; i # SIZE; i%%.

cout ## >Student IH6 > ## id[i]

## > a@erage6 > ## a@erage[i]## > grade6 > ## grade[i]## endl;


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(Program Continues)


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@ro ram 7!1- (Continued)


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#he 'ours and Ca )ate arrays are related throu h their subscripts :


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7.7 Arrays as ?unction Ar uments


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Arrays as ?unction Ar uments

#o pass an array to a function/ just use the arrayname:

s'o9Scores-tests.;

#o define a function that ta9es an arrayparameter/ use empty [] for array ar ument:@oid s'o9Scores-int [].;

&& unction Crotot Ce@oid s'o9Scores-int tests[].

&& unction 'eader


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Arrays as ?unction Ar uments

>hen passin an array to a function/ it is commonto pass array si&e so that function 9no$s ho$ manyelements to process:

s'o9Scores-tests, ())(*+SIZE.; Array si&e must also be reflected in prototype/

header:@oid s'o9Scores-int [], int.;

&& unction Crotot Ce

@oid s'o9Scores-int tests[], int si8e.&& unction 'eader

7!0


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(Program Continues)


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@ro ram 7!10 (Continued)


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Modifyin Arrays in ?unctions

Array names in functions are li9ereference variables * chan es made toarray in a function are reflected in actualarray in callin function

3eed to e,ercise caution that array is notinadvertently chan ed by a function


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7.#$o!Dimensional Arrays


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#$o!Dimensional Arrays

6an define one array for multiple sets ofdata

"i9e a table in a spreadsheet

se t$o si&e declarators in definition:

const int ) :S = , D BS = 3;

int eJams[) :S][D BS]; ?irst declarator is number of ro$sF

second is number of columns

#$o!Dimensional Array


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#$o!Dimensional ArrayGepresentation

const int ) :S = , D BS = 3; inteJams[) :S][D BS];

se t$o subscripts to access element:eJams[2][2] = 4K;

eJams[0][0] eJams[0][1] eJams[0][2]

eJams[1][0] eJams[1][1] eJams[1][2]

e eJams[2][1] eJams[2][2]

columns

r o$s


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7! 7


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-D Array %nitiali&ation

#$o!dimensional arrays are initiali&ed ro$!by!ro$:const int ) :S = 2, D BS = 2;int eJams[) :S][D BS] = 4 , !4 ,

"2, "! ;

6an omit inner / some initial values in a ro$ *array elements $ithout initial values $ill be set to 0 or LBB

4 !4

"2 "!

#$o!Dimensional Array as


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#$o!Dimensional Array as@arameter/ Ar ument

se array name as ar ument in function call:getEJams-eJams, 2.;

se empty [] for ro$/ si&e declarator for column inprototype/ header:const int D BS = 2;&& Mrotot Ce@oid getEJams-int [][D BS], int.;

&& ?eader@oid getEJams-int eJams[][D BS], int ro9s.

l * #h ' 9(


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+,ample * #he s'o9(rra ?unction from @ro ram 7!18


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Ho$ s'o9(rra is 6alled

2 i All th +l t i


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2ummin All the +lements in a#$o!Dimensional Array

iven the follo$in definitions:const int LN+) :S = 5; && umber o ro9sconst int LN+D BS = 5; && umber o columnsint total = 0; && (ccumulatorint numbers[ LN+) :S][ LN+D BS] =

2, !, ", K, , K, 1, 4, ", , , 3, !, 2, " , ", ", 0, 3, 1 , K, 2, !, , 1 ;

2 mmin All the +lements in a


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2ummin All the +lements in a#$o!Dimensional Array

&& Sum t'e arra elementsor -int ro9 = 0; ro9 # LN+) :S; ro9%%.

or -int col = 0; col # LN+D BS; col%%.

total %= numbers[ro9][col];

&& HisCla t'e sumcout ## >/'e total is > ## total ## endl;

2ummin the Go$s of a


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2ummin the Go$s of a#$o!Dimensional Array

iven the follo$in definitions:const int LN+S/LHE /S = 3;const int LN+SD )ES = 5;double total; && (ccumulatordouble a@erage; && /o 'old a@erage scoresdouble scores[ LN+S/LHE /S][ LN+SD )ES] = 44, "!, !", 4K, " , 4K, "1, !4, !", 4 , 42, !3, !!, 42, 4" ;

umm n t e o$s o a


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umm n t e o$s o a#$o!Dimensional

Array&& Oet eac' student s a@erage scoreor -int ro9 = 0; ro9 # LN+S/LHE /S; ro9%%. && Set t'e accumulator total = 0; && Sum a ro9 or -int col = 0; col # LN+SD )ES; col%%. total %= scores[ro9][col]; && Oet t'e a@erage a@erage = total & LN+SD )ES; && HisCla t'e a@erage cout ## >Score a@erage or student > ## -ro9 % 1. ## > is > ## a@erage ##endl;

2ummin the 6olumns of a


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2ummin the 6olumns of a#$o!Dimensional Array

iven the follo$in definitions:const int LN+S/LHE /S = 3;const int LN+SD )ES = 5;double total; && (ccumulatordouble a@erage; && /o 'old a@erage scoresdouble scores[ LN+S/LHE /S][ LN+SD )ES] = 44, "!, !", 4K, " , 4K, "1, !4, !", 4 , 42, !3, !!, 42, 4" ;

2ummin the 6olumns of a


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2ummin the 6olumns of a#$o!Dimensional Array

&& Oet t'e class a@erage or eac' scoreor -int col = 0; col # LN+SD )ES; col%%.

&& )eset t'e accumulator total = 0; && Sum a column or -int ro9 = 0; ro9 # LN+S/LHE /S; ro9%%. total %= scores[ro9][col]; && Oet t'e a@erage a@erage = total & LN+S/LHE /S; && HisCla t'e class a@erage cout ## >Dlass a@erage or test > ## -col % 1. ## > is > ## a@erage ## endl;


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7.8 Arrays $ith #hree or More

Dimensions

Arrays $ith #hree or More


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Arrays $ith #hree or MoreDimensions

6an define arrays $ith any number ofdimensions:

s'ort rectSolid[2][3][5];double timeOrid[3][ ][3][ ];

>hen used as parameter/ specify all but

1st

dimension in prototype/ headin :@oid get)ectSolid-s'ort [][3][5].;


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7.11%ntroduction to the 2#" @ector


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%ntroduction to the 2#" @ector

A data type defined in the 2tandard#emplate "ibrary 'covered more in6hapter 1 (

6an hold values of any type:@ector#int$ scores;

Automatically adds space as more isneeded * no need to determine si&e atdefinition

6an use [] to access elements


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Declarin Vectors

Eou must Pinclude#@ector$ Declare a vector to hold int element:

@ector#int$ scores;

Declare a vector $ith initial si&e ; :@ector#int$ scores-30.;

Declare a vector and initiali&e all elements to :@ector#int$ scores-30, 0.;

Declare a vector initiali&ed to si&e and contentsof another vector:

@ector#int$ inals-scores.;


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Addin +lements to a Vector

se Cus'+bac< member function to addelement to a full array or to an array thathad no defined si&e:

scores Cus'+bac


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Gemovin Vector +lements

se CoC+bac< member function to remove lastelement from vector:

scores CoC+bac


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Cther seful Member ?unctions

Member?unction

Description +,ample

at-elt. Geturns the value of the element atposition elt in the vector

cout ##@ec1 at-i.;

caCacit -. Geturns the ma,imum number ofelements a vector can store $ithoutallocatin more memory

maJelts =@ec1 caCacit -.;

re@erse-. Geverse the order of the elementsin a vector

@ec1 re@erse-.;

resi8e-elts,@al.

Add elements to a vector/optionally initiali&es them

@ec1 resi8e-5,0.;

s9aC-@ec2. +,chan e the contents of t$ovectors

@ec1 s9aC-@ec2.;

Chapter 07 Arrays

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