Types of Data Structures

January 26, 2025 | Data Structures

Data structures are the backbone of computer science — they determine how data is stored, organized, and accessed efficiently.
They can be broadly classified into three main categories based on how elements are arranged and related to each other.

1. Linear Data Structures

In linear data structures, elements are arranged in a sequential manner — one after another.
Each element is connected to its previous and next element, allowing traversal in a straight line.

Common Examples

• Array → A fixed-size collection of elements stored in contiguous memory.
• Linked List → A collection of nodes, each pointing to the next node.
• Stack → Follows LIFO (Last In, First Out) — like a stack of plates.
• Queue → Follows FIFO (First In, First Out) — like a waiting line.
• Deque → Double-ended queue, where you can insert or delete from both ends.

Example

// Stack example (LIFO)
const stack = [];
stack.push(1);
stack.push(2);
stack.push(3);
console.log(stack.pop()); // 3
console.log(stack.pop()); // 2

Key idea: Data elements are ordered and accessed sequentially.

2. Non-Linear Data Structures

In non-linear data structures, data elements are not stored sequentially.
Each element can connect to multiple others, forming hierarchical or network-like relationships.

Common Examples

• Tree → Represents hierarchical relationships (e.g., folders, organization charts).
• Graph → Represents networks and relationships (e.g., social media connections, maps).
• Heap → A specialized tree structure used in priority queues.

Example

// Simple tree node
class Node {
  constructor(value) {
    this.value = value;
    this.children = [];
  }
}

const root = new Node("A");
root.children.push(new Node("B"), new Node("C"));
root.children[0].children.push(new Node("D"));

/*
Tree structure:
    A
   / \\
  B   C
 /
D
*/

Key idea: Data is connected in multiple directions, not just linearly.

3. Hash-Based Data Structures

Hash-based structures use a hash function to compute an index (or hash code) where data is stored.
They provide fast lookups, insertions, and deletions — usually in constant time (O(1)).

Common Examples

• Hash Table / Hash Map → Stores key-value pairs.
• Set / HashSet → Stores unique elements for fast existence checks.

Example

// Hash Map example
const userAges = new Map();
userAges.set("Alice", 25);
userAges.set("Bob", 30);

console.log(userAges.get("Alice")); // 25
console.log(userAges.has("Charlie")); // false

Key idea: Uses hashing to quickly locate data using keys.

Comparison Summary

Understanding the main categories of data structures helps you choose the right one for the problem at hand:

• Use linear structures for ordered data and sequential processing.
• Use non-linear structures for hierarchical or network relationships.
• Use hash-based structures when you need fast, key-based lookups.

Each category offers unique advantages — mastering them is key to writing efficient and scalable code.