meljun cortes c++_chap5

8/10/2019 MELJUN CORTES C++_Chap5

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C Programming Language

Chap. 5

Exploring Arrays and Strings

MELJUN CORTES MBA MPA BSCS


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School of Computer I nformation 2

Objectives

Well learn Declare one-dimensional arrays

Use strings

Create multidimensional arrays Initialize arrays

Build arrays of strings


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1. Declare one-dimensional arrays

Arrays ? A list of variables that are all of the same type and are

accessed through a common name.

Form a convenient way to handle groups of related data.

The general form of one-dimensional Array

type: data type

var_name: array name

size: the number of elements

type var_name[size];


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Declaration of Array type var_name[size];

ex) int grade[5];

grade[0], grade[1], . . . , grade[4]

Index : 0 ~ Size 1

var_name[index]corresponds to a variable.

index range of array[n] : ( 0 ~ n-1 )

Often mistake for ( 1 ~ n )

It can have an fatal effect on the program.



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Declaration of Array



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Usually using array for ( i = 0 ; i < N ; i++ )

a[i] = 0 ; /* clear a */

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

scanf("%d", &a[i]) ;/* reads data into a */

for ( i = 0 ; i < N ; i++ )sum += a[i] ; /* sums the elements of a */



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The scores array

int scores[9];





#include

int main(void) {

int sqrs[10];

int i;

for(i=1; i





Using array When you want to use scanf() to input a numeric value into

an array element, simply put the & in front of the array

name.

Ex) This call to scanf() reads an integer into count[9]

In C, you may not assign one entire array to another

Ex) This fragment is incorrect

scanf("%d", &count[9]) ;

char a1[10], a2[10] ;

: :

a2 = a1 ; /* this is wrong */

for(t=0; t




Example 1.

Arrays are very useful when lists of information need to be

managed.





Example 2.

This program loads a1with the numbers 1 through 10 and then

copies them into a2.





Example 3.

The user first enters the message, which is stored in a character

array. When the user presses ENTER, the entire message is then

encoded by adding 1 to letter.





2. Initialize Arrays

You can give the elements of arrays initial values.

Integer array

int i[5] = { 1, 4, 9, 16, 25 } ;

Character array char a[3] = { 'A', 'B', 'C' } ;

char i[5] = "Herb" ;

type array-name[size] = {value-list};

value-list: a comma-separated list of constants that are

type compatible with the base type of the array.





You can give the elements of arrays initial values.





/* Squares array */

#include

#define ARY_SIZE 5

void main () {

int i;int sqrAry[ARY_SIZE];

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

sqrAry[i] = i * i;

printf("Element\tSquare\n");

printf("=======\t======\n");

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

printf("%5d\t%4d\n", i, sqrAry[i]);

}

Result

Element Square

======= ======

0 01 1

2 4

3 9

4 16





Exercises

Write a program that reads ten numbers entered by the user

and reports if any of them match.

====== Mapping Checking Program ======

Enter ten numbers : 1 2 3 4 5 6 7 8 9 10

Enter a mapping number : 5

5 is in your array[4].


12 is not in your array.


===== Good Bye ~~!! =====




3. Use String

String The most common use of the one-dimensional array in C is

the string.

A string is defined as a null-terminated character array.

The size of array must have one byte larger than the largest

string.

String constant

A series of characters is surrounded by double quotation

mark()

This is a string, Hello, xyz 123

End of a string mark : null character

\0ASCII value is 0.




3. Use String

Storing string and characters




3. Use String

String and character array




3. Use String

String and characters




3. Use String

String variables C language doesnt have string type.

String variables use char array.

char str[11];

char str[11] = Good Day;

char month[] = January;

char *pStr = Good Day!;

char str[10] = {G,o,o,d,,D,a,y,!,\0};


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3. Use String

Cs standard library functions for string gets(str) : reads characters until you press ENTER.

strcpy(to, from) : is used copy the contents frominto to.

strcat(to, from) : concatenates a copy offromto toand

terminates fromwith a null.

strcmp(s1, s2) : lexicographically compares two strings and

returns an integer based on the outcome

- s1 is less than s2 less than 0

- s1 is equal to s2 0

- s1 is greater than s2 greater than 0

strlen(str) : returns the length of the string pointed to by str


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3. Use String

String input

#include

int main(void) {

char str[80];

int i;

printf("Enter a string (less than 80 chars) : \n");

gets(str); /* input the string */

for(i=0; str[i]; i++)

printf("%c", str[i]); /* output the string */

return 0;

}


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3. Use String

String input

#include

int main(void) {

char str[80];

int i;

printf("Enter a string (less than 80 chars) : \n");

gets(str); /* input the string */

printf(str); /* output the string */

return 0;

}


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3. Use String

String input/output function

Using gets() and puts()

gets() reads characters until you press ENTER.

scanf() reads characters until you press blank, space or

ENTER.

puts(message); printf(%s, message);

gets(message); scanf(%s, message);


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3. Use String

String input function


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3. Use String

String output function


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3. Use String

String output function

#include

#define MAXCHARS 81

void main(void) {char message[MAXCHARS]; /* enough storage for a complete line */

printf("Enter a string:\n");

gets(message);

printf("The string just entered is:\n");puts(message);

}

Enter a string:

This is a test input of a string.

The string just entered is:

This is a test input of a string.

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3. Use String

String manipulation functionString manipulation library :

String Length : strlen()function

Returns the length, in characters, of a string

str(parameters)

strlen(str) : 8char str[12];

int strlen(str)

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3. Use String

String manipulation functionString Copy : strcpy()function

Copys the contents of fromto to.

strcpy(to, from) ;

char str[80];

strcpy(str, hello);

printf(str);

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3. Use String

String Copy

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3. Use String

String manipulation functionString Concatenation : strcat()function

Adds the contents of fromto the contents of to.

strcat(to, from) ;

char str[80];

strcpy(str, hello);

strcat(str, there);printf(str)

;

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3. Use String

String Concatenation

3 U St i


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3. Use String

String Compare : strcmp()function

Returns the result of comparison two strings.

strcmp(s1, s2) ;

string1 string2 Size Results Returns

ABC123

ABC123

ABC123

ABC123

ABC123

ABC

ABC123

ABC123

ABC456

ABC456

ABC

ABC

ABC123

123ABC

8

3

4

3

4

3

-1

equal

equal

String1string2

equal

equal

0

0

< 0

0

> 0

0

0

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3. Use String

Return : 0

Return : < 0

Return : > 0

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Example String manipulation function

3. Use String

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Example String manipulation function

3. Use String

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3. Use String

Exercises

Write a program that repeatedly inputs string.

Each time a string is input, concatenate it with a second string

called bigstr.

Add newlines to the end of each string.

If the user types quit, stop inputting and display bigstr(which will

contain a record of all strings input).Also stop if bigstr will be overrun by the next concatenation.

4 Multidimensional Arrays


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4. Multidimensional Arrays

Multidimensional Array

You can create arrays of two or more dimensions``

ex) 10 X 12 two-dimensional integer array

Two-dimensional array

5 X 4 two-dimensional array

int count[10][12] ;



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Two-dimensional Array

This program loads a 4X5

array with the products of

the indices, then displays

the array in row, column

format.

0 0 0 0 0

0 1 2 3 4

0 2 4 6 8

0 3 6 9 12



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Initialization of Multidimensional Array

int table[5][4] = {0, 1, 2, 3, 10, 11, 12, 13, 20, 21, 22, 23,

30, 31, 32, 33, 40, 41, 42, 43};

int table[5][4] = {{0, 1, 2, 3}, {10, 11, 12, 13},

{20, 21, 22, 23}, {30, 31, 32, 33},{40, 41, 42, 43}

};

int table[ ][4] = {{0, 1, 2, 3}, {10, 11, 12, 13},

{20, 21, 22, 23}, {30, 31, 32, 33},

{40, 41, 42, 43}

};

int table[5][4] = {0}; All zero



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Three-Dimensional Array

Add the size of the additional dimension.

ex) 5 X 4 X 3 three-dimensional array

float values[5][4][3] ;



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Example




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Exercises

Write a program that defines a 3X3X3 three-dimensional array,

and load it with the numbers 1 to 27.

And display the sum of its elements.

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