MELJUN CORTES C++ chapter 5 arrays strings

Exploring Arrays and Exploring Arrays and StringsStrings

C Programming C Programming LanguageLanguage

MELJUN CORTESMELJUN CORTES

MELJUN CORTES, MELJUN CORTES, MBA,MPA,BSCSMBA,MPA,BSCS

School of Computer InformationSchool of Computer Information 2

ObjectivesObjectives

WeWe’’ll learnll learn Declare one-dimensional arraysDeclare one-dimensional arrays Use stringsUse strings Create multidimensional arraysCreate multidimensional arrays Initialize arraysInitialize arrays Build arrays of stringsBuild arrays of strings



1.1. Declare one-dimensional arraysDeclare one-dimensional arrays

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

through a common name.through a common name. Form a convenient way to handle groups of related data.Form a convenient way to handle groups of related data.

The general form of one-dimensional ArrayThe general form of one-dimensional Array

typetype : data type : data type var_namevar_name : array name : array name sizesize : the number of elements : the number of elements

type var_name[size]; type var_name[size];



Declaration of ArrayDeclaration of Array type var_name[size];type var_name[size];

ex) int grade[5];ex) int grade[5];

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

Index : Index : 00 ~ ~ Size Size –– 1 1 var_name[index]var_name[index] corresponds to a variable. corresponds to a variable. index range of array[n] : ( index range of array[n] : ( 0 ~ n-10 ~ n-1 ) )

Often mistake for ( Often mistake for ( 1 ~ n1 ~ n ) )

⇒ It can have an fatal effect on the program.It can have an fatal effect on the program.




Declaration of ArrayDeclaration of Array




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

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

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

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

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

sum += a[i] ;sum += a[i] ; /* sums the elements of a *//* sums the elements of a */





The scores arrayThe scores array

int scores[9];int scores[9];




#include <stdio.h> int main(void) {

int sqrs[10];int i;

for(i=1; i<11; i++) sqrs[i-1] = i*i;for(i=0; i<10; i++) printf("%d ", sqrs[i]);

return 0; }


int sqrs[10];int i;

for(i=1; i<11; i++) sqrs[i-1] = i*i;for(i=0; i<10; i++) printf("%d ", sqrs[i]);

return 0; }

Using arrayUsing array This program loads theThis program loads the sqrs sqrs array with the squares of the array with the squares of the

numbers 1 through 10 and then displays them.numbers 1 through 10 and then displays them.




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

array element, simply put the & in front of the array name. array element, simply put the & in front of the array name. Ex) This call to scanf() reads an integer into count[9]Ex) This call to scanf() reads an integer into count[9]

In C, you may not assign one entire array to anotherIn C, you may not assign one entire array to another Ex) This fragment is incorrectEx) This fragment is incorrect

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

char a1[10], a2[10] ; : : a2 = a1 ; /* this is wrong */

char a1[10], a2[10] ; : : a2 = a1 ; /* this is wrong */

for(t=0; t<SIZE; t++)

a2[t] = a1[t];

for(t=0; t<SIZE; t++)

a2[t] = a1[t];



Example 1.Example 1. Arrays are very useful when lists of information need to be managed.Arrays are very useful when lists of information need to be managed.




Example 2.Example 2. This program loads This program loads a1a1 with the numbers 1 through 10 and then copies with the numbers 1 through 10 and then copies

them into them into a2a2..




Example 3.Example 3. The user first enters the message, which is stored in a character array. The user first enters the message, which is stored in a character array.

When the user presses When the user presses ENTERENTER, the entire message is then encoded by , the entire message is then encoded by adding 1 to letter.adding 1 to letter.




2. Initialize Arrays2. Initialize Arrays

You can give the elements of arrays initial values. You can give the elements of arrays initial values.

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

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

char i[5] = "Herb" ;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.

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. You can give the elements of arrays initial values.




/* Squares array */#include <stdio.h>#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 0 1 1 2 4 3 9 4 16




ExercisesExercises

Write a program that reads ten numbers entered by the user

and reports if any of them match.

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 10Enter a mapping number : 55 is in your array[4].Enter a mapping number : 1212 is not in your array.Enter a mapping number : 0===== Good Bye ~~!! =====

====== Mapping Checking Program ======Enter ten numbers : 1 2 3 4 5 6 7 8 9 10Enter a mapping number : 55 is in your array[4].Enter a mapping number : 1212 is not in your array.Enter a mapping number : 0===== Good Bye ~~!! =====



3. Use String3. Use String

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

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

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

String constantString constant A series of characters is surrounded by double quotation A series of characters is surrounded by double quotation

markmark((“”“”)) ““This is a stringThis is a string””, , ““HelloHello””, , ““xyz 123xyz 123””

End of a string mark : null character End of a string mark : null character ‘‘\0\0’’ ASCII value is 0. ASCII value is 0.




Storing string and charactersStoring string and characters




String and character arrayString and character array




String and charactersString and characters




String variablesString variables C language doesnC language doesn’’t have string type.t have string type. String variables use char array.String variables use char array.

char str[11];char str[11]; char str[11] = char str[11] = ““Good DayGood Day””;; char month[] = char month[] = ““JanuaryJanuary””;; char *pStr = char *pStr = ““Good Day!Good Day!””;; char str[10] = {char str[10] = {‘‘GG’’,,’’oo’’,,’’oo’’,,’’dd’’,,’’ ’’,,’’DD’’,,’’aa’’,,’’yy’’,,’’!!’’,,’’\0\0’’};};




CC’’s standard library functions for strings standard library functions for string gets(str)gets(str) : reads characters until you press ENTER.: reads characters until you press ENTER. strcpy(to, from)strcpy(to, from) : is used copy the contents : is used copy the contents fromfrom into into toto.. strcat(to, from)strcat(to, from) : concatenates a copy of: concatenates a copy of from from to to toto and and

terminates terminates fromfrom with a null. with a null. strcmp(s1, s2)strcmp(s1, s2) : lexicographically compares two strings and: lexicographically compares two strings and

returns an integer based on the outcomereturns an integer based on the outcome

- - s1 is less than s2 s1 is less than s2 less than 0less than 0

- s1 is equal to s2 - s1 is equal to s2 00

- s1 is greater than s2 - s1 is greater than s2 greater than 0greater than 0 strlen(str)strlen(str) : returns the length of the string pointed to by str: returns the length of the string pointed to by str




String inputString input


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; }


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; }




String inputString input


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; }


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; }




String input/output functionString input/output function Using gets() and puts()Using gets() and puts()

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

puts(message); printf(“%s”, message);gets(message); ≠ scanf(“%s”, message);

puts(message); printf(“%s”, message);gets(message); ≠ scanf(“%s”, message);




String input functionString input function




String output functionString output function




String output functionString output function

#include <stdio.h>#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);}

#include <stdio.h>#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.

Enter a string:This is a test input of a string.The string just entered is:This is a test input of a string.




String manipulation functionString manipulation function String manipulation library : String manipulation library : <string.h><string.h>

String Length : String Length : strlen()strlen() function function

Returns the length, in characters, of a stringReturns the length, in characters, of a string

str… (parameters)

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

int strlen(str)




String manipulation functionString manipulation function String Copy : String Copy : strcpy()strcpy() function function

Copys the contents of Copys the contents of fromfrom to to toto..

strcpy(to, from) ;

char str[80];

strcpy(str, “hello”);printf(str);




String Copy String Copy




String manipulation functionString manipulation function String Concatenation : String Concatenation : strcat()strcat() function function

Adds the contents of Adds the contents of fromfrom to the contents of to the contents of toto..

strcat(to, from) ;

char str[80];

strcpy(str, “hello”);strcat(str, “ there”);printf(str);




String Concatenation String Concatenation




String Compare : String Compare : strcmp()strcmp() function function

Returns the result of comparison two strings.Returns the result of comparison two strings.

strcmp(s1, s2) ;

string1 str ing2 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

String1<string2

equal

String1>string2

equal

equal

0

0

< 0

0

> 0

0

0




Return : 0

Return : < 0

Return : > 0



Example Example –– String manipulation functionString manipulation function




Example Example –– String manipulation functionString manipulation function





ExercisesExercises

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.

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 Arrays4. Multidimensional Arrays

Multidimensional ArrayMultidimensional Array You can create arrays of two or more dimensions`You can create arrays of two or more dimensions` `̀

ex) 10 X 12 two-dimensional integer arrayex) 10 X 12 two-dimensional integer array

Two-dimensional arrayTwo-dimensional array 5 X 4 two-dimensional array5 X 4 two-dimensional array

int count[10][12] ; int count[10][12] ;




Two-dimensional ArrayTwo-dimensional Array This program loads a 4X5 This program loads a 4X5

array with the products of array with the products of

the indices, then displays the indices, then displays

the array in row, column the array in row, column

format.format.

0 0 0 0 0 0 1 2 3 4 0 2 4 6 8 0 3 6 9 12

0 0 0 0 0 0 1 2 3 4 0 2 4 6 8 0 3 6 9 12




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

30, 31, 32, 33, 40, 41, 42, 43}; 30, 31, 32, 33, 40, 41, 42, 43}; int table[5][4] = int table[5][4] = {{0, 1, 2, 3}, {10, 11, 12, 13},{{0, 1, 2, 3}, {10, 11, 12, 13},

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

int table[ ][4] = int table[ ][4] = {{0, 1, 2, 3}, {10, 11, 12, 13},{{0, 1, 2, 3}, {10, 11, 12, 13}, {20, 21, 22, 23}, {30, 31, 32, 33}, {20, 21, 22, 23}, {30, 31, 32, 33}, {40, 41, 42, 43}{40, 41, 42, 43} };};

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




Three-Dimensional ArrayThree-Dimensional Array Add the size of the additional dimension.Add the size of the additional dimension.

ex) 5 X 4 X 3 three-dimensional arrayex) 5 X 4 X 3 three-dimensional array

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



ExampleExample





ExercisesExercises

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.

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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MELJUN CORTES C++ chapter 5 arrays strings

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