arrays ce 102 algorithms and programming kto karatay university arrays are data structures...

Arrays

CE 102 Algorithms and Programming KTO Karatay University

• Arrays are data structures consisting of data items of the same type

• Arrays are not dynamic entities

• they remain the same size once they are created

• they don’t grow or shrink as the program executes

Arrays


-45

6

0

72

1543

-89

0

62

-3

1

6453

-78arr[ 11 ]

arr[ 10 ]

arr[ 9 ]

arr[ 8]

arr[ 7 ]

arr[ 4 ]

arr[ 3 ]

arr[ 2 ]

arr[ 1 ]

arr[ 0 ]

arr[ 6 ]

arr[ 5 ]

Position number (index or subscript) of the element within array “arr”

Name of array (Note that all elements of this array have the same name, “arr”arr”)

First element is at index “0”

Declaring Arrays

When defining arrays, specifyWhen defining arrays, specify• NameName• Type of arrayType of array• Number of elementsNumber of elements

arrayType arrayName[ numberOfElements ];arrayType arrayName[ numberOfElements ];• Examples:Examples:

int c[ 10 ]; int c[ 10 ];

float myArray[ 3284 ];float myArray[ 3284 ]; Defining multiple arrays of same typeDefining multiple arrays of same type

• Format similar to regular variablesFormat similar to regular variables• Example:Example:

int int aa[ 100 ], [ 100 ], bb[ 27 ];[ 27 ];


Declaring Arrays

InitializersInitializers

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

• If not enough initializers, rightmost elements become 0If not enough initializers, rightmost elements become 0

int n[ 5 ] = { 0 } int n[ 5 ] = { 0 } All elements 0All elements 0

• If too manyIf too many,, a syntax error is produced a syntax error is produced

int n[ 5 ] = { 0int n[ 5 ] = { 0, 5, -7, 9, 2, 1, 8, 5, -7, 9, 2, 1, 8 } }

If size If size is is omitted, initializers determine itomitted, initializers determine it

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

• 5 initializers, therefore 5 element array5 initializers, therefore 5 element array


Example – Declaring and Using Arrays


Example – Using Arrays as Index and Histogram Printing


Character Arrays

SStrings are in fact sequences of characters, we cantrings are in fact sequences of characters, we can represent them also represent them also as plain arrays of char elements.as plain arrays of char elements.

For example, the following array:For example, the following array:char name[20]char name[20]

is an array that can store up to 20 elements of type char. It can be is an array that can store up to 20 elements of type char. It can be shown shown as:as:

In this array, In this array, we can store sequences of characters up to 20 characters we can store sequences of characters up to 20 characters long.long.

But we can also store shorter sequences.But we can also store shorter sequences. A special character is A special character is used to used to signalsignal the end of the valid sequence: the the end of the valid sequence: the

null characternull character which can be written as which can be written as ‘‘\0’\0’

name

D e e t \0m

D e e t F i l i z \0m


Character Arrays

Initializing on declaration:Initializing on declaration:

char myword [] = { 'H', 'e', 'l', 'l', 'o', '\0' }; char myword [] = "Hello"; //initialization by a literal

A literal can not be assigned to char array after the declaration:A literal can not be assigned to char array after the declaration:

char text[10];text = “some text”;text = {‘H’,‘i’,‘/0’};

Content of char array can be modified letter by letter after initializationContent of char array can be modified letter by letter after initialization::

char text[30] = "Here is some text!";printf(“%s\n”,text);text[13] = 'w';text[14] = 'i';text[15] = 'n';text[16] = 'e'; printf(“%s\n”,text);


Character Arrays


• ExampleExample

char string1[] = "first";char string1[] = "first"; Null character '\0' terminates stringsNull character '\0' terminates strings string1 actually has 6 elementsstring1 actually has 6 elements

• It is equivalent toIt is equivalent to

char string1[] = { 'f', 'i', 'r', 's', 't', '\0' };char string1[] = { 'f', 'i', 'r', 's', 't', '\0' };

• Can access individual charactersCan access individual characters

string1[ 3 ] is character ‘s’string1[ 3 ] is character ‘s’

• Array name is address of array, so Array name is address of array, so ““&&”” not needed for scanf not needed for scanf

scanf( "%s", string2 );scanf( "%s", string2 ); Reads characters until whitespace encounteredReads characters until whitespace encountered Can write beyond end of array, be carefulCan write beyond end of array, be careful

Example - Character Arrays


Passing Arrays to Functions


Passing arraysPassing arrays• To pass an array argument to a function, specify the name To pass an array argument to a function, specify the name

of the array without any brackets of the array without any brackets

int myArray[ 24 ];int myArray[ 24 ];

myFunction( myArray, 24 );myFunction( myArray, 24 ); Array size usually passed to function Array size usually passed to function

• Arrays passed call-by-reference Arrays passed call-by-reference • Name of array is address of first elementName of array is address of first element• Function knows where the array is storedFunction knows where the array is stored

Modifies original memory locationsModifies original memory locations Passing array elements Passing array elements

• Passed by call-by-valuePassed by call-by-value• Pass subscripted name (i.e., myArray[ 3 ]) to functionPass subscripted name (i.e., myArray[ 3 ]) to function

Passing Arrays to Functions

Function prototypeFunction prototype

void modifyArray( int b[], int arraySize );void modifyArray( int b[], int arraySize );

• Parameter names optional in prototypeParameter names optional in prototype int b[] could be written int []int b[] could be written int [] int arraySize could be simply intint arraySize could be simply int

void modifyArray(int [], int)void modifyArray(int [], int)


Example – Array “Name” is equal to &Name[0]


Example – Passing Arrays to Functions


Example – const type qualifier with arrays


Sorting Arrays


Sorting dataSorting data• Important computing applicationImportant computing application• Virtually every organization must sort some data Virtually every organization must sort some data

Bubble sort (sinking sort) Bubble sort (sinking sort) • Several passes through the array Several passes through the array • Successive pairs of elements are compared Successive pairs of elements are compared

If increasing order (or identical ), no changeIf increasing order (or identical ), no change If decreasing order, elements exchangedIf decreasing order, elements exchanged

• RepeatRepeat Example:Example:

• original: 3 4 2 6 7original: 3 4 2 6 7• pass 1: 3 2 4 6 7pass 1: 3 2 4 6 7• pass 2: 2 3 4 6 7 pass 2: 2 3 4 6 7 • Small elements "bubble" to the topSmall elements "bubble" to the top

BubbleSort.cBubbleSort.c

Searching Arrays : Linear Search

Search an array for a Search an array for a key valuekey value Linear searchLinear search

• Simple Simple • Compare each element of array with key valueCompare each element of array with key value• Useful for small and unsorted arraysUseful for small and unsorted arrays

• Example Example LinearSearch.c LinearSearch.c


Searching Arrays : Binary Search

Binary search Binary search • For sorted arraysFor sorted arrays• Compares middle element with keyCompares middle element with key

If equal, match foundIf equal, match found If key < middle, looks in first half of arrayIf key < middle, looks in first half of array If key > middle, looks in last halfIf key > middle, looks in last half RepeatRepeat

• Very fast; at most n steps, where 2Very fast; at most n steps, where 2nn > number of elements > number of elements 30 element array takes at most 5 steps30 element array takes at most 5 steps

• 2255 > 30 so at most 5 steps > 30 so at most 5 steps

BinarySearch.cBinarySearch.c


Multi-dimensional Arrays

Multidimensional arrays can be described as "arrays Multidimensional arrays can be described as "arrays of arrays".of arrays".

A two dimentional (2D) array can be imagined as a A two dimentional (2D) array can be imagined as a table made of elements all having the same data table made of elements all having the same data typetype

Arrays can be 1D, 2D, 3D or even more...Arrays can be 1D, 2D, 3D or even more...• 2D array having size 3x5 has 15 elements2D array having size 3x5 has 15 elements• 3D array having size 4x5x3 has 60 elements 3D array having size 4x5x3 has 60 elements • As dimension increase, array size grows quicklyAs dimension increase, array size grows quickly



Decleration of a 2D array:Decleration of a 2D array:• int matrix[3][5];int matrix[3][5];

• type name[row_size][column_size];type name[row_size][column_size];

Access to elements: matrix[1][3] = 12;Access to elements: matrix[1][3] = 12;



Row 0

Row 1

Row 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


Array Initialization

int a[3][4] = {1,2,3,4,5,6,7,8,9,0,1,2};int a[3][4] = {1,2,3,4,5,6,7,8,9,0,1,2};

int b[3][4] = {{1,2,3,4},{5,6,7,8},{9,0,1,2}};int b[3][4] = {{1,2,3,4},{5,6,7,8},{9,0,1,2}};

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

1

5

9

2

6

0

3

7

1

4

8

2

1

5

0

2

6

0

3

0

0

4

0

0

• Examples Examples ArrayInitialization.c ArrayInitialization.cStudentGrades.cStudentGrades.c

• UUnspecified elements nspecified elements are are set to zeroset to zero


Multi-dimensional Arrays (3D)

Decleration of a 3D array:Decleration of a 3D array:• int cube[4][4][4];int cube[4][4][4];• type name[row_size][column_size][depth_size];type name[row_size][column_size][depth_size];

Access to elements:

cube[2][3][0] = 8;cube[0][3][2] = 5;cube[0][1][3] = 6;

depth

columns

rows

6

8

5

6

8

5


Homework-2


Write a C program that calculates mean, median and mode of an array entered by the user.

Mean Mean –– average average Median Median –– number in middle of sorted list number in middle of sorted list

• 1, 2, 3, 4, 5 1, 2, 3, 4, 5

• 3 is the median3 is the median Mode Mode –– number that occurs most often number that occurs most often

• 1, 1, 1, 2, 3, 3, 4, 5 1, 1, 1, 2, 3, 3, 4, 5

• 1 is the mode1 is the mode

The program will display the histogram of the array after finding the mode.

arrays ce 102 algorithms and programming kto karatay university arrays are data structures...

Documents

array arrname of array

array s

end of array

content of char array

following array

array argument

plain arrays of char

char myword