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Array & Strings

{C}

Programming

Programming for Problem Solving (PPS)

GTU # 3110003

USING

Prof. Nilesh Gambhava

�Computer Engineering Department,�Darshan Institute of Engineering & Technology, Rajkot

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Need of Array Variable

Suppose we need to store rollno of the student in the integer variable.

Now we need to store rollno of 100 students.

This is not appropriate to declare these many integer variables.

e.g. 100 integer variables for rollno.

Solution to declare and store multiple variables of similar type is an array.
An array is a variable that can store multiple values.

int rollno;

Declaration

int rollno101, rollno102, rollno103, rollno104...;

Declaration

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Definition: Array

An array is a fixed size sequential collection of elements of same data type grouped under single variable name.

int rollno[100];

[0]	[1]	[2]	…	[99]

Fixed Size
Here, the size of an array is 100 (fixed) to store rollno

Sequential
It is indexed to 0 to 99 in sequence

Same Data type
All the elements (0-99) will be integer variables

Single Name
All the elements (0-99) will be referred as a common name rollno

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Declaring an array

By default array index starts with 0.
If we declare an array of size 5 then its index ranges from 0 to 4.
First element will be store at mark[0] and last element will be stored at mark[4] not mark[5].
Like integer and float array we can declare array of type char.

data-type variable-name[size];

Syntax

int mark[5];

Integer Array

integer

[0]	[1]	[2]	[3]	[4]

float avg[5];

Float Array

float

[0]	[1]	[2]	[3]	[4]

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Initialing and Accessing an Array

int mark=90; //variable mark is initialized with value 90

printf("%d",mark); //mark value printed

Declaring, initializing and accessing single integer variable

int mark[5]={85,75,76,55,45}; //mark is initialized with 5 values

printf("%d",mark[0]); //prints 85

printf("%d",mark[1]); //prints 75

printf("%d",mark[2]); //prints 65

printf("%d",mark[3]); //prints 55

printf("%d",mark[4]); //prints 45

Declaring, initializing and accessing integer array variable

[0]	[1]	[2]	[3]	[4]
85	75	65	55	45

mark[5]

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Read(Scan) Array Elements

void main()

{

int mark[5];

printf("Enter array element=");

scanf("%d",&mark[0]);

printf("Enter array element=");

scanf("%d",&mark[1]);

printf("Enter array element=");

scanf("%d",&mark[2]);

printf("Enter array element=");

scanf("%d",&mark[3]);

printf("Enter array element=");

scanf("%d",&mark[4]);

� printf("%d",mark[0]);

printf("%d",mark[1]);

printf("%d",mark[2]);

printf("%d",mark[3]);

printf("%d",mark[4]);

}

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Reading array without loop

void main()

{

int mark[5],i;

for(i=0;i<5;i++)

{

printf("Enter array element=");

scanf("%d",&mark[i]);

}

for(i=0;i<5;i++)

{

printf("%d",mark[i]);

}

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Reading array using loop

[0]	[1]	[2]	[3]	[4]
85	75	65	55	45

mark[5]

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Develop a program to count number of positive or negative number from an array of 10 numbers.

void main(){

int num[10],i,pos,neg;

pos = 0;

neg = 0;

for(i=0;i<10;i++)

{

printf("Enter array element=");

scanf("%d",&num[i]);

}

for(i=0;i<10;i++)

{

if(num[i]>0)

pos=pos+1;

else

neg=neg+1;

}

printf("Positive=%d,Negative=%d",pos,neg);

}

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Program

Enter array element=1

Enter array element=2

Enter array element=3

Enter array element=4

Enter array element=5

Enter array element=-1

Enter array element=-2

Enter array element=3

Enter array element=4

Enter array element=5

Positive=8,Negative=2

Output

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#3110003 (PPS) – Array and Strings

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Develop a program to read n numbers in an array and print them in reverse order.

void main()

{

int num[100],n,i;

printf("Enter number of array elements=");

scanf("%d",&n);

//loop will scan n elements only

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

{

printf("Enter array element=");

scanf("%d",&num[i]);

}

//negative loop to print array in reverse order

for(i=n-1;i>=0;i--)

{

printf("%d\n",num[i]);

}

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Program

Enter number of array elements=5

Enter array element=1

Enter array element=2

Enter array element=3

Enter array element=4

Enter array element=5

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Output

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Practice Programs

Develop a program to calculate sum of n array elements in C.
Develop a program to find largest array element in C.

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void main()

{

int a[100],i,n,sum=0;

printf("Enter size of the array : ");

scanf("%d",&n);

printf("Enter elements in array : ");

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

{

scanf("%d",&a[i]);

}

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

{

sum+=a[i]; //sum=sum+a[i];

}

printf("sum of array is : %d",sum);

getch();

}

Enter size of the array: 5

Enter elements in array: 7

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sum of an array is:33

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#include <stdio.h>

void main()

{

//Initialize array

int arr[] = {25, 11, 7, 75, 56};

//Calculate length of array arr

int length = sizeof(arr)/sizeof(arr[0]);

//Initialize max with first element of array.

int max = arr[0];

//Loop through the array

for (int i = 0; i < length; i++) {

//Compare elements of array with max

if(arr[i] > max)

max = arr[i];

}

printf("Largest element present in given array: %d\n", max);

getch();

}

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Multi Dimensional Array

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Declaring 2 Dimensional Array

A two dimensional array can be seen as a table with ‘x’ rows and ‘y’ columns.
The row number ranges from 0 to (x-1) and column number ranges from 0 to (y-1).

data-type variable-name[x][y];

Syntax

int data[3][3]; //This array can hold 9 elements

Declaration

	Column-0	Column-1	Column-2
Row-0	data[0][0]	data[0][1]	data[0][2]
Row-1	data[1][0]	data[1][1]	data[1][2]
Row-2	data[2][0]	data[2][1]	data[2][2]

int data[3][3];

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Initialing and Accessing a 2D Array: Example-1

int data[3][3] = {

{1,2,3}, //row 0 with 3 elements

{4,5,6}, //row 1 with 3 elements

{7,8,9} //row 2 with 3 elements

};

printf("%d",data[0][0]); //1

printf("%d",data[0][1]); //2

printf("%d\n",data[0][2]); //3

�printf("%d",data[1][0]); //4

printf("%d",data[1][1]); //5

printf("%d\n",data[1][2]); //6

printf("%d",data[2][0]);//7

printf("%d",data[2][1]); //8

printf("%d",data[2][2]); //9

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Program

// data[3][3] can be initialized like this also

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

	Column-0	Column-1	Column-2
Row-0	1	2	3
Row-1	4	5	6
Row-2	7	8	9

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Initialing and Accessing a 2D Array: Example-2

int data[2][4] = {

{1,2,3,4}, //row 0 with 4 elements

{5,6,7,8}, //row 1 with 4 elements

};

printf("%d",data[0][0]); //1

printf("%d",data[0][1]); //2

printf("%d",data[0][2]); //3

printf("%d\n",data[0][3]); //4

�printf("%d",data[1][0]); //5

printf("%d",data[1][1]); //6

printf("%d",data[1][2]); //7

printf("%d",data[1][3]); //8

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// data[2][4] can be initialized like this also

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

	Col-0	Col-1	Col-2	Col-3
Row-0	1	2	3	4
Row-1	5	6	7	8

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Read(Scan) 2D Array Elements

void main(){

int data[3][3],i,j;

for(i=0;i<3;i++)

{

for(j=0;j<3;j++)

{

printf("Enter array element=");

scanf("%d",&data[i][j]);

}

for(i=0;i<3;i++)

{

for(j=0;j<3;j++)

{

printf("%d",data[i][j]);

}

printf("\n");

}

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Program

Enter array element=1

Enter array element=2

Enter array element=3

Enter array element=4

Enter array element=5

Enter array element=6

Enter array element=7

Enter array element=8

Enter array element=9

123

456

789

Output

Prof. Nilesh Gambhava

#3110003 (PPS) – Array and Strings

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Develop a program to count number of positive, negative and zero elements from 3 X 3 matrix

void main(){

int data[3][3],i,j,pos=0,neg=0,zero=0;

for(i=0;i<3;i++)

{

for(j=0;j<3;j++)

{

printf("Enter array element=");

scanf("%d",&data[i][j]);

if(data[i][j]>0)

pos=pos+1;

else if(data[i][j]<0)

neg=neg+1;

else

zero=zero+1;

}

printf("positive=%d,negative=%d,zero=%d",pos,neg,zero);

}

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Program

Enter array element=9

Enter array element=5

Enter array element=6

Enter array element=-3

Enter array element=-7

Enter array element=0

Enter array element=11

Enter array element=13

Enter array element=8

positive=6,negative=2,zero=1

Output

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Practice Programs

Develop a program to perform addition of two matrix.
Develop a program to perform multiplication of two matrix.

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#include<stdio.h>

#include<conio.h>

void main()

{

int mat1[3][3], mat2[3][3], i, j, mat3[3][3];

printf("Enter 3*3 matrix 1 elements :");

for(i=0; i<3; i++)

{

for(j=0; j<3; j++)

scanf("%d",&mat1[i][j]);

}

printf("Enter 3*3 matrix 2 elements :");

for(i=0; i<3; i++)

{

for(j=0; j<3; j++)

scanf("%d",&mat2[i][j]);

}

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printf("\nAdding the two matrix.....");

for(i=0; i<3; i++)

{

for(j=0; j<3; j++)

mat3[i][j]=mat1[i][j]+mat2[i][j];

}

printf("\nBoth matrix added successfully!");

printf("\nHere is the new matrix:\n");

for(i=0; i<3; i++)

{

for(j=0; j<3; j++)

printf("%d ",mat3[i][j]);

printf("\n");

}

getch();

}

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String�(Character Array)

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Definition: String

A String is a one-dimensional array of characters terminated by a null('\0').

Each character in the array occupies one byte of memory, and the last character must always be null('\0').
The termination character ('\0') is important in a string to identify where the string ends.

char name[10];

[0]	[1]	[2]	…	[9]

name[10]

[0]	[1]	[2]	[3]	[4]	[5]	[6]	[7]	[8]	[9]
c	h	i	r	a	g	b	\0

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Declaring & Initializing String

char name[10];

Declaration

char name[10]={'c','h','i','r','a','g','b','\0'};

Initialization method 1:

char name[10]="chiragb";

//'\0' will be automatically inserted at the end in this type of declaration.

Initialization method 2:

name[10]

[0]	[1]	[2]	[3]	[4]	[5]	[6]	[7]	[8]	[9]
c	h	i	r	a	g	b	\0

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Read String: scanf()

There is no need to use address of (&) operator in scanf to store a string.
As string name is an array of characters and the name of the array, i.e., name indicates the base address of the string (character array).
scanf() terminates its input on the first whitespace(space, tab, newline etc.) encountered.

void main()

{

char name[10];

printf("Enter name:");

scanf("%s",name);

printf("Name=%s",name);

}

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Program

Enter name: chirag

Name=chirag

Output

Enter name: city ahmedabad

Name=city

Output

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Read String: gets()

gets(): Reads characters from the standard input and stores them as a string.
puts(): Prints characters from the standard.
scanf(): Reads input until it encounters whitespace, newline or End Of File(EOF) whereas gets() reads input until it encounters newline or End Of File(EOF).
gets(): Does not stop reading input when it encounters whitespace instead it takes whitespace as a string.

#include<stdio.h>

void main()

{

char name[10];

printf("Enter name:");

gets(name); //read string including white spaces

printf("Name=%s",name);

}

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Program

Enter name:city ahmedabad

Name=city ahmedabad

Output

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String Handling Functions : strlen()

C has several inbuilt functions to operate on string. These functions are known as string handling functions.
strlen(s1): returns length of a string in integer

#include <stdio.h>

#include <string.h> //header file for string functions

void main()

{

char s1[10];

printf("Enter string:");

gets(s1);

printf("%d",strlen(s1)); // returns length of s1 in integer

}

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Enter string:chirag name

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Output

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String Handling Functions: strcmp()

strcmp(s1,s2): Returns 0 if s1 and s2 are the same.
Returns less than 0 if s1<s2.
Returns greater than 0 if s1>s2.

void main()

{

char s1[10],s2[10];

printf("Enter string-1:");

gets(s1);

printf("Enter string-2:");

gets(s2);

if(strcmp(s1,s2)==0)

printf("Strings are same");

else

printf("Strings are not same");

}

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Program

Enter string-1:Computer

Enter string-2:Computer

Strings are same

Output

Enter string-1:Computera

Enter string-2:Computerb

Strings are not same

Output

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String Handling Functions

For examples consider: char s1[]="Their",s2[]="There";

Syntax	Description
strcpy(s1,s2)	Copies 2^nd string to 1^st string. strcpy(s1,s2) copies the string s2 in to string s1 so s1 is now “There”. s2 remains unchanged.

strcat(s1,s2)	Appends 2^nd string at the end of 1^st string. strcat(s1,s2); a copy of string s2 is appended at the end of string s1. Now s1 becomes “TheirThere”

strchr(s1,c)	Returns a pointer to the first occurrence of a given character in the string s1. printf("%s",strchr(s1,'i')); Output : ir

strstr(s1,s2)	Returns a pointer to the first occurrence of a given string s2 in string s1. printf("%s",strstr(s1,"he")); Output : heir

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String Handling Functions (Cont…)

For examples consider: char s1[]="Their",s2[]="There";

Syntax	Description
strrev(s1)	Reverses given string. strrev(s1); makes string s1 to “riehT”

strlwr(s1)	Converts string s1 to lower case. printf("%s",strlwr(s1)); Output : their

strupr(s1)	Converts string s1 to upper case. printf("%s",strupr(s1)); Output : THEIR

strncpy(s1,s2,n)	Copies first n character of string s2 to string s1 s1=""; s2="There"; strncpy(s1,s2,2); printf("%s",s1); Output : Th

strncat(s1,s2,n)	Appends first n character of string s2 at the end of string s1. strncat(s1,s2,2); printf("%s", s1); Output : TheirTh

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String Handling Functions (Cont…)

For examples consider: char s1[]="Their",s2[]="There";

Syntax	Description
strncmp(s1,s2,n)	Compares first n character of string s1 and s2 and returns similar result as strcmp() function. printf("%d",strcmp(s1,s2,3)); Output : 0

strrchr(s1,c)	Returns the last occurrence of a given character in a string s1. printf("%s",strrchr(s2,'r')); Output : re

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Thank you

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