Data structures are an essential concept in computer science and programming. They provide a way to organize and store data efficiently, allowing for faster access and manipulation. In this article, we will explore what data structures are and the different classifications of data structures.

## What is a Data Structure?

A data structure is a way of organizing and storing data in a computer’s memory. It defines the way data is organized and how operations can be performed on that data. It helps in efficient storage, retrieval, and manipulation of data.

Data structures can be linear or non-linear. Linear data structures organize elements in a sequential manner, while non-linear structures allow for more complex relationships between elements.

## Different Classifications of Data Structures

### 1. Primitive Data Structures

Primitive data structures are the most basic types provided by programming languages. These include integer, floating-point numbers, characters, and booleans. They are atomic and cannot be further divided into smaller components.

### 2. Arrays

An array is a linear data structure that stores a collection of elements of the same type. Each element has an index associated with it, which allows for fast access to any element based on its position.

**Example:**

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

### 3. Linked Lists

A linked list consists of nodes where each node contains a value and a reference to the next node in the sequence. Unlike arrays, linked lists do not require contiguous memory allocation.

**Example:**

class Node { int value; Node next; }

### 4. Stacks

A stack is a linear data structure that follows the Last-In-First-Out (LIFO) principle. Elements are added or removed from only one end, known as the top of the stack.

**Example:**

Stack<Integer> stack = new Stack<>(); stack.push(1); stack.push(2); stack.pop(); // Removes 2

### 5. Queues

A queue is a linear data structure that follows the First-In-First-Out (FIFO) principle. Elements are added at one end, known as the rear, and removed from the other end, known as the front.

**Example:**

Queue<Integer> queue = new LinkedList<>(); queue.add(1); queue.add(2); queue.remove(); // Removes 1

### 6. Trees

Trees are non-linear data structures with a hierarchical organization of elements. They consist of nodes connected by edges, where each node can have zero or more child nodes.

**Example:**

class Node { int value; Node left; Node right; }

### 7. Graphs

A graph is a non-linear data structure consisting of vertices and edges. Vertices represent entities, and edges represent relationships between those entities.

**Example:**

class Graph { List<Vertex> vertices; List<Edge> edges; }

### 8. Hash Tables

A hash table, also known as a hash map, is a data structure that stores data in key-value pairs. It uses a hash function to compute an index into an array of buckets or slots, from which the desired value can be found.

**Example:**

Map<String, Integer> hashMap = new HashMap<>(); hashMap.put("apple", 5); hashMap.put("banana", 3); int count = hashMap.get("apple"); // Retrieves 5

## Conclusion

Data structures are crucial for efficient data storage and manipulation. Understanding different types of data structures and their classifications is essential for any programmer or computer scientist. By using appropriate data structures, you can optimize your code and improve the efficiency of your applications.

Now that you have a good understanding of different classifications of data structures, you can choose the most appropriate one based on your requirements and solve complex problems efficiently.