Array in Data Structure
Array in Data Structure
Arrays are defined as the collection of similar types of data items
stored at contiguous memory locations. It is one of the simplest data
structures where each data element can be randomly accessed by using its index
number.
In C programming, they are the derived data types that can store the
primitive type of data such as int, char, double, float, etc. For example, if
we want to store the marks of a student in 6 subjects, then we don't need to define
a different variable for the marks in different subjects. Instead, we can
define an array that can store the marks in each subject at the contiguous
memory locations.
Properties of array
There are some of the properties of an array that are listed as follows
-
- Each
element in an array is of the same data type and carries the same size
that is 4 bytes.
- Elements
in the array are stored at contiguous memory locations from which the
first element is stored at the smallest memory location.
- Elements
of the array can be randomly accessed since we can calculate the address
of each element of the array with the given base address and the size of
the data element.
Representation of an array
We can represent an array in various ways in different programming
languages. As an illustration, let's see the declaration of array in C language-
As per the above illustration, there are some of the following important
points -
- Index starts with 0.
- The array's length is 10, which means we can store 10 elements.
- Each element in the array can be accessed via its index.
Why are arrays required?
Arrays are useful because -
- Sorting and searching a value in an array is easier.
- Arrays are best to process multiple values quickly and easily.
- Arrays are good for storing multiple values in a single variable- In computer programming, most cases require storing a large number of data of a similar type. To store such an amount of data, we need to define a large number of variables. It would be very difficult to remember the names of all the variables while writing the programs. Instead of naming all the variables with a different name, it is better to define an array and store all the elements into it.
Memory allocation of an array
As stated above, all the data elements of an array are stored at
contiguous locations in the main memory. The name of the array represents the
base address or the address of the first element in the main memory. Each
element of the array is represented by proper indexing.
We can define the indexing of an array in the below ways -
- 0 (zero-based indexing): The first element of the array will be arr[0].
- 1 (one-based indexing): The first element of the array will be arr[1].
- n (n - based indexing): The first element of the array can reside at any random index number.
In the above image, we have shown the memory allocation of an array arr
of size 5. The array follows a 0-based indexing approach. The base address of
the array is 100 bytes. It is the address of arr[0]. Here, the size of the data
type used is 4 bytes; therefore, each element will take 4 bytes in the memory.
How to access an element from the array?
We required the information given below to access any random element
from the array -
Base Address of the array.
Size of an element in bytes.
Type of indexing, array follows.
The formula to calculate the address to access an array element -
Byte address of element A[i] =
base address + size * ( i - first index)
Here, size represents the memory taken by the primitive data types. As
an instance, int takes 2 bytes, float takes 4 bytes of memory space in C
programming.
We can understand it with the help of an example -
Suppose an array, A[-10 ..... +2 ] having Base address (BA) = 999 and
size of an element = 2 bytes, find the location of A[-1].
L(A[-1]) = 999 + 2 x [(-1) - (-10)]
= 999 + 18
= 1017
Basic operations
Now, let's discuss the basic operations supported in the array -
- Traversal - This operation is used to print the elements of the array.
- Insertion - It is used to add an element at a particular index.
- Deletion - It is used to delete an element from a particular index.
- Search - It is used to search an element using the given index or by the value.
- Update - It updates an element at a particular index.
Traversal operation
This operation is performed to traverse through the array elements. It
prints all array elements one after another. We can understand it with the
below program -
#include <stdio.h>
void main() {
int Arr[5] = {18, 30, 15, 70,
12};
int i;
printf("Elements of the
array are:\n");
for(i = 0; i<5; i++) {
printf("Arr[%d] =
%d, ", i, Arr[i]);
}
}
Output
Insertion operation
This operation is performed to insert one or more elements into the
array. As per the requirements, an element can be added at the beginning, end,
or at any index of the array. Now, let's see the implementation of inserting an
element into the array.
#include <stdio.h>
int main()
{
int arr[20] = { 18, 30, 15,
70, 12 };
int i, x, pos, n = 5;
printf("Array elements
before insertion\n");
for (i = 0; i < n;
i++)
printf("%d ",
arr[i]);
printf("\n");
x = 50; // element to be
inserted
pos = 4;
n++;
for (i = n-1; i >= pos;
i--)
arr[i] = arr[i - 1];
arr[pos - 1] = x;
printf("Array elements
after insertion\n");
for (i = 0; i < n;
i++)
printf("%d ",
arr[i]);
printf("\n");
return 0;
}
Output
Deletion operation
As the name implies, this operation removes an element from the array
and then reorganizes all of the array elements.
#include <stdio.h>
void main() {
int arr[] = {18, 30, 15, 70,
12};
int k = 30, n = 5;
int i, j;
printf("Given array
elements are :\n");
for(i = 0; i<n; i++) {
printf("arr[%d] =
%d, ", i, arr[i]);
}
j = k;
while( j < n) {
arr[j-1] = arr[j];
j = j + 1;
}
n = n -1;
printf("\nElements of
array after deletion:\n");
for(i = 0; i<n; i++) {
printf("arr[%d] =
%d, ", i, arr[i]);
}
}
Output
Search operation
This operation is performed to search an element in the array based on
the value or index.
#include <stdio.h>
void main() {
int arr[5] = {18, 30, 15, 70,
12};
int item = 70, i, j=0 ;
printf("Given array
elements are :\n");
for(i = 0; i<5; i++) {
printf("arr[%d] =
%d, ", i, arr[i]);
}
printf("\nElement to be
searched = %d", item);
while( j < 5){
if( arr[j] == item ) {
break;
}
j = j + 1;
}
printf("\nElement %d is
found at %d position", item, j+1);
}
Output
Update operation
This operation is performed to update an existing array element located
at the given index.
#include <stdio.h>
void main() {
int arr[5] = {18, 30, 15, 70,
12};
int item = 50, i, pos = 3;
printf("Given array
elements are :\n");
for(i = 0; i<5; i++) {
printf("arr[%d] =
%d, ", i, arr[i]);
}
arr[pos-1] = item;
printf("\nArray elements
after updation :\n");
for(i = 0; i<5; i++) {
printf("arr[%d] =
%d, ", i, arr[i]);
}
}
Output
Complexity of Array operations
Time and space complexity of various array operations are described in
the following table.
Time Complexity
Operation Average Case Worst Case
Access O(1) O(1)
Search O(n) O(n)
Insertion O(n) O(n)
Deletion O(n) O(n)
Space Complexity
In array, space complexity for worst case is O(n).
Advantages of Array
- Array provides the single name for the group of variables of the same type. Therefore, it is easy to remember the name of all the elements of an array.
- Traversing an array is a very simple process; we just need to increment the base address of the array in order to visit each element one by one.
- Any element in the array can be directly accessed by using the index.
Disadvantages of Array
- Array is homogenous. It means that the elements with similar data type can be stored in it.
- In array, there is static memory allocation that is size of an array cannot be altered.
- There will be wastage of memory if we store less number of elements than the declared size.
Conclusion
In this article, we have discussed the special data structure, i.e.,
array, and the basic operations performed on it. Arrays provide a unique way to
structure the stored data such that it can be easily accessed and can be
queried to fetch the value using the index.
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