DSA Arrays

 DSA Arrays – Complete Beginner Guide

An Array is one of the most basic and important data structures in Data Structures & Algorithms (DSA).
Almost every DSA topic starts with arrays, so understanding them clearly is very important for exams & interviews.

What is an Array?

An array is a data structure that:

• Stores multiple values

• Of the same data type

• In contiguous memory locations

• Accessed using an index

Example:

 Characteristics of Arrays

•  Fixed size
• Same data type
•  Fast access (O(1))
• Uses index starting from 0
•  Size cannot change easily

Types of Arrays

 1. One-Dimensional Array (1D)

Stores elements in a single line.

 2. Two-Dimensional Array (2D)

Stores data in rows and columns (matrix).

 Basic Array Operations

 1. Traversal (Access all elements)

Algorithm (Traversal):

1. Start

2. For i = 0 to n-1

   • Print arr[i]

3. Stop

 Time Complexity: O(n)

 2. Insertion

Insert an element at a given position.

Algorithm (Insert at position):

1. Shift elements to the right

2. Insert new value

3. Increase size

 Time Complexity: O(n)

 3. Deletion

Remove an element from a position.

Algorithm (Delete at position):

1. Shift elements to the left

2. Reduce size

 Time Complexity: O(n)

 4. Searching

Linear Search

 Time Complexity: O(n)

Binary Search (Sorted Array)

 Time Complexity: O(log n)

 5. Updating

Change value at an index.

 Time Complexity: O(1)

Advantages of Arrays

•  Fast element access
•  Simple to use
•  Efficient for fixed-size data
•  Cache-friendly

Disadvantages of Arrays

•  Fixed size
•  Insertion & deletion are slow
•  Memory wastage or overflow
•  Cannot store different data types

Real-Life Examples of Arrays

• Marks of students

• Temperature readings

• Daily sales data

• Player scores

Array vs Linked List

Common Array Problems (DSA)

•  Find maximum / minimum
•  Reverse an array
•  Sum of elements
• Remove duplicates
• Find missing number
• Rotate array

 These are very common interview questions.

 Common Beginner Mistakes

•  Index out of bounds
•  Confusing index & position
•  Assuming dynamic resizing
• Wrong loop conditions

 Exam / Interview Questions (Arrays)

Q1. What is an array?
 Collection of same type elements in contiguous memory

Q2. What is array index?
 Position of element (starts from 0)

Q3. Why is array traversal O(n)?
 Every element is visited once

Summary

•  Array stores same type elements
•  Uses contiguous memory
•  Fast access using index
•  Traversal, insertion, deletion are core operations
• Foundation of DSA
•  Must-know for exams & interviews