Data Structures11 min read

Arrays and Linked Lists: Choosing the Right Structure

Understand arrays and linked lists - the most fundamental data structures. Learn when to use arrays vs linked lists, their time complexities, and practical implementations. Essential knowledge for every developer.

Robert Kim

December 18, 2025

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Arrays and linked lists are the foundation of data structures. Understanding them deeply helps you understand everything else. Let's learn when to use each and why it matters.

Arrays Explained

Arrays store elements in contiguous memory. Accessing any element is instant (O(1)), but inserting or deleting in the middle is slow (O(n)). Arrays are perfect when you need fast random access.

Linked Lists Explained

Linked lists store elements as nodes connected by pointers. Inserting or deleting is fast (O(1) at known position), but accessing elements is slow (O(n)). Linked lists are perfect when you do lots of insertions and deletions.

When to Use Which?

Use arrays when you need fast access by index, know the size in advance, or need cache-friendly memory layout. Use linked lists when you do lots of insertions/deletions, size is unknown, or memory is fragmented.

Time Complexity Comparison

I'll show you the time complexities for common operations - access, search, insertion, deletion. Understanding these helps you choose the right structure for your problem.

Implementation Examples

I'll walk you through implementing both from scratch. Seeing how they work internally makes everything click.

#Data Structures#Arrays#Linked Lists#Algorithms

Common Questions & Answers

What's the difference between arrays and linked lists?

Arrays store elements in contiguous memory with O(1) access but O(n) insertion/deletion in middle. Linked lists use nodes with pointers, providing O(1) insertion/deletion at known position but O(n) access. Arrays are better for random access, linked lists for frequent insertions/deletions.

javascript

Run Explain

// Array - contiguous memory
const arr = [1, 2, 3, 4, 5];
arr[2];           // O(1) - instant access
arr.push(6);       // O(1) - add to end
arr.splice(2, 1);  // O(n) - remove from middle

// Linked List - nodes with pointers
class Node {
  constructor(value) {
    this.value = value;
    this.next = null;
  }
}

class LinkedList {
  constructor() {
    this.head = null;
  }
  
  // O(1) - insert at beginning
  prepend(value) {
    const node = new Node(value);
    node.next = this.head;
    this.head = node;
  }
  
  // O(n) - access by index
  get(index) {
    let current = this.head;
    for (let i = 0; i < index; i++) {
      current = current.next;
    }
    return current.value;
  }
}

When should I use arrays vs linked lists?

Use arrays when you need fast random access, know size in advance, or need cache-friendly access patterns. Use linked lists when you do frequent insertions/deletions, size is unknown, or memory is fragmented. Arrays are better for most cases, linked lists for specific scenarios.