Array

ARRAY – Short Notes

🔹 Definition

An array is a collection of similar data types stored in contiguous memory locations and accessed using an index.

Example:
int arr[5] = {10, 20, 30, 40, 50};

🔹 Key Characteristics

• Stores homogeneous data (same data type)
• Fixed size (size must be defined at creation)
• Elements are stored in continuous memory
• Indexing usually starts from 0
• Fast access using index (O(1))

🔹 Types of Arrays

1. One-Dimensional Array (1D)

Stores elements in a single row.

Example:

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

2. Two-Dimensional Array (2D)

Used to store data in rows and columns (matrix form).

Example:

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

3. Multi-Dimensional Array

Arrays with more than two dimensions (rarely used).

🔹 Declaration & Initialization

Declaration

datatype arrayName[size];

Initialization

int a[3] = {10, 20, 30};

🔹 Accessing Array Elements

Using index:

a[0] = 10;
printf("%d", a[1]);

🔹 Memory Representation

• If base address = B
• Size of each element = w
• Address of arr[i] =
  
  B + (i × w)

🔹 Common Array Operations

🔹 Advantages

✅ Fast access

✅ Easy to use

✅ Efficient for storing fixed-size data

🔹 Disadvantages

❌ Fixed size

❌ Memory wastage possible

❌ Insertion & deletion are costly

❌ Cannot store different data types

🔹 Applications of Arrays

• Searching & Sorting algorithms
• Matrix operations
• Stack & Queue implementation
• Graphs and Dynamic Programming
• Storing large datasets