C Programming Tutorial
'C' Arrays are fixed length Data Structure.Arrays represent collection of Data of same data type, Memory will be allocated as a contiguoes block.
C Arrays has lower bound and upper bound,upper bound must be specified at the time of declaration, otherwise error. Lower bound starts from 0.
It is a Linear Data Structure, elements can be accessed in Linear fashion.
C Arrays are Random access Data Structure, any elements can be accessed randomly.
Fixed Number of items , such as collection of products,cities,courses,seats in Bus or train or flight etc.,, can be represented as an Array.
It is a homogenious datatype,all elements should be of same type.
'C' Language supports one-dimensional and multi-dimensional arrays
Array Syntax:
datatype variable[expr]; /* here expr is a subscript, this value can be a Integer constant, or constant integral expression,must be +ve number */
Array Declartion in 'C' :example:
int a[10] ;
short s[10];
char c[10];
float f[10];
or it can be declared using constant value #define MAX-SIZE 10 int a[MAX-SIZE]
or it can be declared using constant integral expression #define MAX-SIZE 10 int a[MAX-SIZE/2+1]In Array sqaure brackets [] contain subscript
Initialize an Array
int a[3]={0} /* Initialize all 3 elements with 0 */
int a[3]={1,5,7} /* Initialize all 3 elements with 1,5,7 */
char a[3]={'a','b','c'}
float a[3]={10.00,5.77,7.99}
error: variable-sized object may not be initialized 8 | int c[n+m]={0};
Array Example: sum of all elements
#include <stdio.h>
int main()
{
int a[5]={1,4,5,3,1};
int sum=0;
for (int i=0; i < sizeof(a)/sizeof(int); i++){
sum+=a[i];
}
printf("sum of array=%d",sum);
}
output:
sum of array=14
Print Array Elements using recursion
void printArray(int a[],int len)
{
static int i=0;
if(len==0)return;
printf("%d ",a[i++]);
printArray(a,--len);
}
C Language supports Multi-Dimensional Arrays i.e arrays of arrays.single sqaure brackets is single dimensional array, double square brackets makes two-dimensional arrays, 3 sqaure brackets leads to 3-dimensional arrays. and so on...
Declaring Two-Dimensional Array
int a[2][2];
// a is a 2 dimensional array which has 2 rows and 2 columns
internally array "a" represented as
column0 column1
row 0 a[0][0] a[0][1]
row 1 a[1][0] a[1][1]
first subscript represents "row" second subscript represents "column".
Number of elements in 2-dimesional arrays is "n*m" , n=rows m= columns
Fill 2-Dimensional Array with Static Data
a[0][0]=10; a[0][1]=13; a[1][0]=20; a[1][1]=24;Fill 2-Dimensional Array with Dynamic Data
int n=2,m=3;
int a[n][m];
printf("Reading values from keyboard\n");
for(int row=0; row < n; row++)
{
for(int col=0; col < m; col++)
{
scanf("%d",&a[row][col]);
}
}
Display Array Elements
printf("Displaying Array Elements\n");
for(int row=0; row < n; row++)
{
for(int col=0; col < m; col++)
{
printf("%d ",a[row][col]);
}
printf("\n");
}
Input and Output
Reading values from keyboard 1 2 3 4 5 6 Displaying Array Elements 1 2 3 4 5 6 //second input, user can enter all values in single line. Reading values from keyboard 1 2 3 4 5 6 Displaying Array Elements 1 2 3 4 5 6
Initializing 2-Dimensional Array
int a[2][3]={1}; all elements filled with 1
int a[2][3]={1,2,3,4,5,6};First three numbers will go to row 0, next three elements go to row 1
int a[2][3]={{10,20,30},{40,50,60} };In this style of initialization, row 0 has {10,20,30} row 1 has {40,50,60}
int n=2,m=3;
int a[n][m]={{10,20,30},{40,50,60} };
error: variable-sized object may not be initialized
Adding 2 matrix requires, matrix should have same number of rows and columns.
int a[2][2]={{10,20},{30,40}};
int b[2][2]={{30,40},{10,20}};
printf("Matrix sum\n");
for(int i=0; i < 2; i++){
for(int j=0; j < 2; j++){
printf("%d ",a[i][j]+b[i][j]);
}
printf("\n");
}
ouput:
Matrix sum 40 60 40 60
A sparse matrix is a matrix that is comprised of mostly zero values
Sparse matrices are distinct from matrices with mostly non-zero values, which are referred to as dence matrices.
The sparcity of a matrix can be qualified with a score, which is the number of zero values in the matrix divided by the total number of elements in the matrix.
sparcity = count zero elements / total number of elements
1 0 0 1 0 0 0 0 2 0 0 1 0 0 0 2 0 0 the matrix has 13 zero values of the 18 elements. giving this matrix a sparcity score is 13/18 = 0.722 or about 72%.
Sparse matrices can cause problems with regards to space and time complexity
passing arrays to functions as a argument is nothing but passing base address of the array, In case of Multi-dimensional arrays first Dimensional is ignored by the compiler.Remaning all dimesions must be passed to the function
int arr[2][3]={{4,5,6},{10,11,12}};
func(arr,2);
void func(int a[2][3],int ROWS)
{
//find no. of columns
int COLS = sizeof(a[0])/sizeof(a[0][0]);
//display array elements
for(int i=0; i < ROWS; i++)
{
for(int j=0; j < COLS; j++)
{
printf("%d ",a[i][j]);
}
printf("\n");
}
}
calling func(int a[100][3] is accepted by the compiler. Here Row size 100 is ignored by the compiler,matter of fact any number specified is not considered.
‘arr’ as multidimensional array must have bounds for all dimensions except the firstCharacter Arrays are special types of arrays where last character will be NULL character. It can be supplied by programmer or automatically appends NULL character . '\0' or NULL
Declaring Character Arrays
char c[10];
//read characters into array.
for(int i=0; i <10; i++){
scanf("%c",&c[i]);
}
Strings represent sequence of characters null character at the end '\0', null character marks end of the string, Since Strings represent array of characters each element is a single byte ASCII value.
in bitwise operations null character has all bits off.
Find string length
char *p="hello String!";
printf("string=\"%s\" length:%d",p,strlen(p));
int strlen(char*p)
{
int n=0;
while(*p++!='\0')++n;
return n;
}
//output:13
storage size isn't constant, static storage class on arrays
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