contoh array

5/27/2018 Contoh Array

1/25

Dale Roberts

Department of Computer and Information Science,

School of Science, IUPUI

CSCI 230

Arrays

Dale Roberts, Lecturer

IUPUI

[email protected]


2/25Dale Roberts

Arrays

ArrayGroup of consecutive memory locations

Same name and type, ex: an array of integers

To refer to an element, specifyArray name

Position number of particular element in the array

Format:array_name[position number]

First element at position 0nelement array named c:c[ 0 ], c[ 1 ]...c[ n 1]

Example: int my_array[12]

my_array[0]= -45 value storedPosition number must be an integer number or an

integer expressionExample: my_array[1.5] ERROR!!

my_array[i+j] valid ifiand j are integers

Name of array (Note that all

elements of this array have the

same name,my_array)

Position number of the elementwithin arraymy_array

-45

6

0

72

1543

-89

0

62

-3

1

6453

78

My_array[0]

My_array[1]

My_array[2]

My_array[3]

My_array[4]

My_array[5]

My_array[6]

My_array[7]

My_array[8]

My_array[9]

My_array[10]

My_array[11]


3/25Dale Roberts

Arrays (cont.)

Array elements are like normal variablesmy_array[8]= -3;printf( "%d", my_array[8]);

Perform operations in subscript. If xequals 3:my_array[ 5 - 2 ] == my_array[ 3 ] == my_array[ x ]

Declaring Arrays

When declaring arrays, specify

Name

Type of array

Number of elements: arrayType arrayName[ numberOfElements];

Examples:int c[ 100 ];/* reserve memory sufficient enough to store

100elements of type integer */

float myArray[ 3284 ];


4/25Dale Roberts

Arrays (cont.)

Declaring multiple arrays of same type: format similar to regular variablesExample: int b[ 100 ], x[ 27 ];

Arrays may be declared to contain other data typesExample: int a[ 100 ];

float b[ 100 ];

char c[ 100 ]; /* Strings are stored by using character arrays*/

Example:

#include /* a simple program that uses arrays */

main(

{

int i, array_int[100];

for (i=0; i


5/25Dale Roberts

Arrays (cont.)

Initializersint n[5] = {1, 2, 3, 4, 5};

Example:main(){int i, a[10]={1, 2, 3, 4, 5, 6, 7, 8, 9, 10};for (i=0; i


6/25Dale Roberts

1 /* Fig. 6.8: fig06_08.c

2 Histogram printing program */

3 #include

4 #defineSIZE 10

5

6 intmain()

7 {

8 intn[ SIZE ] = { 19, 3, 15, 7, 11, 9, 13, 5, 17, 1 };

9 inti, j;

10

11 printf( "%s%13s%17s\n", "Element", "Value", "Histogram" );

12

13 for( i = 0; i


7/25Dale Roberts

Arrays (cont.)

Example:

#include

#define SIZE 100

main()

{

int i, a[SIZE];

int sum = 0;

for (i=0; i< size; i++)

sum = sum + a[i];

printf(sum: %d\n, sum);

}


8/25Dale Roberts

Character arrays

String is really a static array of characters, ex: firstCharacter arrays can be initialized using string literals

char string1[] = "first";

Null character '\0'terminatesstrings

string1actually has 6 elements

It is equivalent to charstring1[]={'f','i','r','s','t','\0'};

Can access individual charactersstring1[3] is character s

Array name is address of array, so & not needed for scanf charstring2[20];

scanf("%s",string2); /* can read a string with max of size19 and a

null character*/

Reads characters until whitespace (space, tab, carriage-return, newline,vertical tab) encountered

Can write beyond end of array, be careful

Character Arrays

f i r s t \0

Null character (indicates string termination)

&is NOT used, why?


9/25Dale Roberts

Passing Arrays to Functions

Passing arrays

To pass an array argument to a function, specify the name of the arraywithout any bracketsint myArray[24];

...

myFunction(myArray,24);

...

Array size usually passed to functionArrays passed call-by-reference

the called functions can modify the element values in the callers originalarray

Name of array is the address of first element of the array

Function knows where the array is stored. Therefore, when the calledfunction modifies array elements in its function body, it is modifying theactual elements of array in the original memory locations

Pass array name

Size is also often sent as an argument

myArray

main()

myFunction()


10/25Dale Roberts

Passing Arrays to Functions (cont.)

Example: #include main()

{int a[10];printf(a = %p \n &a[0] = %p\n, a, &a[0]);}

output: a = FFEE&a[0] = FFEE

Passing array elements

Individual elements of an array are passed by call-by-valuePass subscripted name (i.e.,myArray[3]) to function

Example: compare(a[0], a[1]);

An array is a vector while individual elements are scalars.

Function prototypevoid modifyArray( int b[], int arraySize );

Parameter names optional in prototype

int b[]could be written int []

int arraySizecould be simply int

will be passed by value


11/25Dale Roberts

1 /* Fig. 6.13: fig06_13.c2 Passing arrays and individual array elements to functions*/3 #include4 #defineSIZE 556 voidmodifyArray( int[], int); /* appears strange */

7 voidmodifyElement( int);89 intmain()10 {11 inta[ SIZE ] = { 0, 1, 2, 3, 4 }, i;1213 printf( "Effects of passing entire array call "14 "by reference:\n\nThe values of the "15 "original array are:\n" );

1617 for( i = 0; i


12/25Dale Roberts

Function

definitions

33

34 voidmodifyArray( intb[], intsize )

35 {

36 intj;

3738 for( j = 0; j


13/25Dale Roberts

Multiple-Dimensional ArraysMultiple subscripted arrays

Arrays require at least two subscripts to identify a

particular elementANSI C standard allows at least 12 array subscripts

2D Arrays

Tables with rows and columns (mby narray)Like matrices: specify row, then column

Row 0Row 1Row 2

Column 0 Column 1 Column 2 Column 3

a[0][0]a[

1

][

0

]

a[2][0]a[0][1]a[

1

][

1

]

a[2][1]a[0][2]a[

1

][

2

]

a[2][2]a[0][3]a[

1

][

3

]

a[2][3]

Row subscript

Array nameColumn subscript

A: scalar A[0]: 1D array

1-Dimensional vector

A[0][0]: (2 subscripts)

2D array (matrix)

2-dimensional vector

A common error is to use

math matrix notation a(1,2)


14/25Dale Roberts

Multiple-Subscripted Arrays

Initialization

int b[2][2] = {{1,2},{3,4}};int c[3][2] = {{1,2},{3,4},{5,6}};

Initializers grouped by row in braces

If not enough, unspecified elements set to zeroint b[2][2]={{1},{3,4}};

Referencing elementsSpecify row, then columnprintf("%d",b[0][1]);

1 2

3 4

1 03 4

1 2

3 4

5 6

1 2 3 4 5 6Actual storage in the memory -

rows by rows -row-major

1 /* Fi 6 22 fi 06 22


15/25Dale Roberts

1 /* Fig. 6.22: fig06_22.c

2 Double-subscripted array example */

3 #include

4 #defineSTUDENTS 3

5 #defineEXAMS 4

6

7 intminimum( constint[][ EXAMS ], int, int);

8 intmaximum( constint[][ EXAMS ], int, int);9 doubleaverage( constint[], int);

10 voidprintArray( constint[][ EXAMS ], int, int);

11

12 intmain()

13 {

14 intstudent;

15 constintstudentGrades[ STUDENTS ][ EXAMS ] =

16 { { 77, 68, 86, 73 },

17 { 96, 87, 89, 78 },

18 { 70, 90, 86, 81 } };

19

20 printf( "The array is:\n" );

21 printArray( studentGrades, STUDENTS, EXAMS );

22 printf( "\n\nLowest grade: %d\nHighest grade: %d\n",

23 minimum( studentGrades, STUDENTS, EXAMS ),24 maximum( studentGrades, STUDENTS, EXAMS ) );

25

26 for( student = 0; student


16/25Dale Roberts

33

34 /* Find the minimum grade */

35 intminimum( constintgrades[][ EXAMS ],

36 intpupils, inttests )

37 {

38 inti, j, lowGrade = 100;

39

40 for( i = 0; i


17/25Dale Roberts

65 inti, total = 0;

66

67 for( i = 0; i


18/25Dale Roberts

Sorting Arrays

Sorting data

Important computing applicationVirtually every organization must sort some data

Bubble sort (sinking sort)

Several passes through the array

Successive pairs of elements are comparedIf increasing order (or identical ), no change

If decreasing order, elements exchanged

Repeat

Example:

original: 3 4 2 6 7pass 1: 3 2 4 6 7

pass 2: 2 3 4 6 7

Small elements "bubble" to the top

ase tu y: omput ng ean e an an


19/25Dale Roberts

ase tu y: omput ng ean, e an anMode Using Arrays

Meanaverage

Mediannumber in middle of sorted listExample: 1, 2, 3, 4, 5 3 is the median

Modenumber that occurs most oftenExample: 1, 1, 1, 2, 3, 3, 4, 5 1 is the mode

1 /* Fig. 6.16: fig06_16.c

2 This program introduces the topic of survey data analysis.

3 It computes the mean, median, and mode of the data */

4 #include

5 #defineSIZE 99

6

7 voidmean( constint[] );

8 voidmedian( int[] );9 voidmode( int[], constint[] ) ;

10 voidbubbleSort( int[] );

11 voidprintArray( constint[] );

12

13 intmain()

14 {

15 intfrequency[ 10 ] = { 0 };

Function prototypes


20/25Dale Roberts

33

34 voidmean( constintanswer[] )

35 {

36 intj, total = 0;

37

38 printf( "%s\n%s\n%s\n", "********", " Mean", "********" );

39

40 for( j = 0; j


21/25

Dale Roberts

Define function median

Sort Array

Print middle element

Define function mode

Increase frequency[]

depending on response[]

65 }

66

67 voidmode( intfreq[], constintanswer[] )

68 {

69 intrating, j, h, largest = 0, modeValue = 0;

70

71 printf( "\n%s\n%s\n%s\n",

72 "********", " Mode", "********" );

73

74 for( rating = 1; rating


22/25

Dale Roberts

95 printf( "\n" );

96 }

9798 printf( "The mode is the most frequent value.\n"

99 "For this run the mode is %d which occurred"

100 " %d times.\n", modeValue, largest );

101}

102

80 printf( "%s%11s%19s\n\n%54s\n%54s\n\n",

81 "Response", "Frequency", "Histogram",

82 "1 1 2 2", "5 0 5 0 5" );

83

84 for( rating = 1; rating largest ) {

88 largest = freq[ rating ];

89 modeValue = rating;

90 }91

92 for( h = 1; h


23/25

Dale Roberts

126

127 printf( "%2d", a[ j ] );

128 }

129 }

103 voidbubbleSort( inta[] )

104 {

105 intpass, j, hold;

106

107 for( pass = 1; pass


24/25

Dale Roberts

Program

Output

Mean********The mean is the average value of the dataitems. The mean is equal to the total ofall the data items divided by the numberof data items (99). The mean value forthis run is: 681 / 99 = 6.8788

********Median

********The unsorted array of responses is7 8 9 8 7 8 9 8 9 7 8 9 5 9 8 7 8 7 86 7 8 9 3 9 8 7 8 7 7 8 9 8 9 8 9 7 8 96 7 8 7 8 7 9 8 9 2 7 8 9 8 9 8 9 7 5 35 6 7 2 5 3 9 4 6 4 7 8 9 6 8 7 8 9 7 87 4 4 2 5 3 8 7 5 6 4 5 6 1 6 5 7 8 7

The sorted array is1 2 2 2 3 3 3 3 4 4 4 4 4 5 5 5 5 5 5 55 6 6 6 6 6 6 6 6 6 7 7 7 7 7 7 7 7 7 77 7 7 7 7 7 7 7 7 7 7 7 7 8 8 8 8 8 8 8

8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 89 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9

The median is element 49 ofthe sorted 99 element array.For this run the median is 7

********Mode********Response Frequency Histogram

1 1 2 25 0 5 0 5

1 1 *2 3 ***3 4 ****4 5 *****5 8 ********6 9 *********7 23 ***********************8 27 ***************************9 19 *******************

The mode is the most frequent value.For this run the mode is 8 which occurred 27 times.


25/25

Dale Roberts

Searching Arrays: Linear Search vs Binary Search

Search an array for a key value

Linear searchSimple

Compare each element of array with key value

Useful for small and unsorted arrays

Binary searchFor sorted arrays

Comparesmiddleelement with keyIf equal, match found

If key < middle, looks in first half of array

If key > middle, looks in last half

Repeat

Very fast; at most nsteps, where 2n> number of elements

30 element array takes at most 5 steps

25> 30 so at most 5 steps

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