Array Data Structure

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Array Data Structure
(Last Updated On: October 6, 2018)

In this DSA tutorial, you will learn what is Array Data Structure and how to use it.

The array is a container which can hold a fixed number of items and these items should be of the same type. Most of the data structures make use of arrays to implement their algorithms. Following are the important terms to understand the concept of Array Data Structure.

  • Element − Each item stored in an array is called an element.
  • Index − Each location of an element in an array has a numerical index, which is used to identify the element.

Array Representation

Arrays can be declared in various ways in different languages. For illustration, let’s take C array declaration.

DSA array declaration

As per the above illustration, the following are the important points to be considered.

  • Index starts with 0.
  • The array length is 10 which means it can store 10 elements.
  • Each element can be accessed via its index. For example, we can fetch an element at index 6 as 9.

Basic Operations

Following are the basic operations supported by an array.

  • Traverse − print all the array elements one by one.
  • Insertion − Adds an element at the given index.
  • Deletion − Deletes an element at the given index.
  • Search − Searches an element using the given index or by the value.
  • Update − Updates an element at the given index.

In C, when an Array Data Structure is initialized with size, then it assigns defaults values to its elements in the following order.

Data Type Default Value
bool false
char0
int0
float0.0
double0.0f
void
wchar_t0

Insertion Operation

Insert operation is to insert one or more data elements into an array. Based on the requirement, a new element can be added at the beginning, end, or any given index of the array.

Here, we see a practical implementation of insertion operation, where we add data at the end of the array −

Algorithm

Let Array be a linear unordered array of MAX elements.

Result

Let LA be a Linear Array (unordered) with N elements and K is a positive integer such that K<=N. Following is the algorithm where ITEM is inserted into the Kth position of LA −

1. Start
2. Set J = N
3. Set N = N+1
4. Repeat steps 5 and 6 while J >= K
5. Set LA[J+1] = LA[J]
6. Set J = J-1
7. Set LA[K] = ITEM
8. Stop

Program to implement insertion of elements

#include <stdio.h>

main() {
int LA[] = {1,3,5,7,8};
int item = 10, k = 3, n = 5;
int i = 0, j = n;

printf("The original array elements are :\n");

for(i = 0; i<n; i++) { printf("LA[%d] = %d \n", i, LA[i]); } n = n + 1; while( j >= k) {
LA[j+1] = LA[j];
j = j – 1;
}

LA[k] = item;
printf("The array elements after insertion :\n");

for(i = 0; i<n; i++) {
printf("LA[%d] = %d \n", i, LA[i]);
}
}

Output

The original array elements are :
LA[0] = 1
LA[1] = 3
LA[2] = 5
LA[3] = 7
LA[4] = 8
The array elements after insertion :
LA[0] = 1
LA[1] = 3
LA[2] = 5
LA[3] = 10
LA[4] = 7
LA[5] = 8

Deletion Operation

Deletion refers to removing an existing element from the array and re-organizing all elements of an array.

Algorithm

Consider LA is a linear array with N elements and K is a positive integer such that K<=N. Following is the algorithm to delete an element available at the Kth position of LA.

1. Start
2. Set J = K
3. Repeat steps 4 and 5 while J < N
4. Set LA[J-1] = LA[J]
5. Set J = J+1
6. Set N = N-1
7. Stop

Program to implement deletion of elements

#include <stdio.h>
main() {
int LA[] = {1,3,5,7,8};
int k = 3, n = 5;
int i, j;

printf("The original array elements are :\n");
for(i = 0; i<n; i++) {
printf("LA[%d] = %d \n", i, LA[i]);
}

j = k;

while( j < n) {
LA[j-1] = LA[j];
j = j + 1;
}

n = n -1;
printf("The array elements after deletion :\n");

for(i = 0; i<n; i++) {
printf("LA[%d] = %d \n", i, LA[i]);
}
}

Output

The original array elements are :
LA[0] = 1
LA[1] = 3
LA[2] = 5
LA[3] = 7
LA[4] = 8
The array elements after deletion :
LA[0] = 1
LA[1] = 3
LA[2] = 7
LA[3] = 8

Search Operation

You can perform a search for an array element based on its value or its index.

Algorithm

Consider LA is a linear array with N elements and K is a positive integer such that K<=N. Following is the algorithm to find an element with a value of ITEM using sequential search.

1. Start
2. Set J = 0
3. Repeat steps 4 and 5 while J < N
4. IF LA[J] is equal ITEM THEN GOTO STEP 6
5. Set J = J +1
6. PRINT J, ITEM
7. Stop

Program to implement searching of elements

#include <stdio.h>
main() {
int LA[] = {1,3,5,7,8};
int item = 5, n = 5;
int i = 0, j = 0;

printf("The original array elements are :\n");

for(i = 0; i<n; i++) {
printf("LA[%d] = %d \n", i, LA[i]);
}

while( j < n){
if( LA[j] == item ) {
break;
}

j = j + 1;
}

printf("Found element %d at position %d\n", item, j+1);
}

Output

The original array elements are :
LA[0] = 1
LA[1] = 3
LA[2] = 5
LA[3] = 7
LA[4] = 8
Found element 5 at position 3

Update Operation

Update operation refers to updating an existing element from the array at a given index.

Algorithm

Consider LA is a linear array with N elements and K is a positive integer such that K<=N. Following is the algorithm to update an element available at the Kth position of LA.

1. Start
2. Set LA[K-1] = ITEM
3. Stop

Program to implement Updation of elements

#include <stdio.h>
main() {
int LA[] = {1,3,5,7,8};
int k = 3, n = 5, item = 10;
int i, j;

printf("The original array elements are :\n");

for(i = 0; i<n; i++) {
printf("LA[%d] = %d \n", i, LA[i]);
}

LA[k-1] = item;

printf("The array elements after updation :\n");

for(i = 0; i<n; i++) {
printf("LA[%d] = %d \n", i, LA[i]);
}
}

Output

The original array elements are :
LA[0] = 1
LA[1] = 3
LA[2] = 5
LA[3] = 7
LA[4] = 8
The array elements after updation :
LA[0] = 1
LA[1] = 3
LA[2] = 10
LA[3] = 7
LA[4] = 8

Data Structures Algorithms Books: Algorithms Plus Data Structures

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