Array in C

Array : The array is a data structure, which can store a fixed-size sequential collection of elements of the same data type.

Syntax:

datatype   array_name [ array_size ] ; 

Examples:

int n[6];

n[ ] is used to denote an array 'n'. It means that 'n' is an array.

We can also declare an array by another method.

int n[ ] = {2, 3, 15, 8, 4, 23};

element	2	3	15	8	4	23
index	0	1	2	3	4	5

Examples:

int mark[5] = {19, 1, 8, 7, 9};

We can also initialize an array like this.

int mark[] = {19, 1, 8, 7, 9};

Example 1: Array Input/Output

#include <stdio.h>

int main()

{

  int a[5];

  printf("Enter 5 integers: ");

  for(int i = 0; i < 5; ++i)

{

     scanf("%d", &a[i]);

   }

   printf("Displaying integers: ");

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

 {

      printf("%d\n", a[i]);

    }

  return 0;

}

Example 2:

#include <stdio.h>

void show(char ch)

{

   printf("%c ", ch);

}

int main()

{

   char arr[ ] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'};

   for (int x=0; x<10; x++)

   {

       show(arr[x]);

   }

   return 0;

}

2D Arrays

Syntax:   datatype array_name[size1][size2];

Example:  

int x[2][4];Here, 'x' is a 2D array of integers which consists of 2 rows and 4 columns.

It is like

	Column[0]	Column[1]	Column[2]	Column[3]
Row[0]	a[0][0]	a[0][1]	a[0][2]	a[0][3]
Row[1]	a[1][0]	a[1][1]	a[1][2]	a[1][3]

Example: 

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

or

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

Let's consider different cases of assigning values to an array at the time of declaration.

int a[2][2] = { 10, 20, 30, 40 };       /* valid */
int a[  ][2] = { 10, 20, 30, 40 };        /* valid */
int a[2][  ] = { 10, 20, 30, 40 };        /* invalid */
int a[  ][  ] = { 10, 20, 30, 40 };        /* invalid */

Multi-dimensional array

Syntax:

datatype array_name[size1][size2]...[sizeN]

Example:

int a[5][10][4];

double c[3][2][4]={

                             {{-0.1, 0.22, 0.3, 4.3}, {2.3, 4.7, -0.9, 2}},

                             {{0.9, 3.6, 4.5, 4}, {1.2, 2.4, 0.22, -1}},

                             {{8.2, 3.12, 34.2, 0.1}, {2.1, 3.2, 4.3, -2.0}}

                              };

Example:

#include<stdio.h>

void show_array(int a[3][3]);

int main()

{

    int a[3][3], i, j;

    printf("Enter 9 numbers for the array: \n");

    for (i = 0; i < 3; ++i)

    {

        for (j = 0; j < 3; ++j)

        {    

            scanf("%d", &a[i][j]);

        }

    }

       show_array(a);

return 0;

}

void show_array(int a[3][3])

{

    int i, j;

    printf("The complete array is: \n");

    for (i = 0; i < 3; ++i)

    {

        printf("\n");           // getting cursor to new line

        for (j = 0; j < 3; ++j)

        {       

           printf("%d\t", a[i][j]);  

        }

}

}

Example 3: Three-dimensional array

#include <stdio.h>

int main()

{

  int a[2][3][2];

  printf("Enter 12 values: \n");

  for (int i = 0; i < 2; ++i)

  {

    for (int j = 0; j < 3; ++j)

    {

      for (int k = 0; k < 2; ++k)

      {

        scanf("%d", &a[i][j][k]);

      }

    }

  }

printf("\n Displaying values:\n"); 

  for (int i = 0; i < 2; ++i)

  {

    for (int j = 0; j < 3; ++j)

    {

      for (int k = 0; k < 2; ++k)

      {

        printf("a[%d][%d][%d] = %d\n", i, j, k, a[i][j][k]);

      }

    }

  }

  return 0;

}