The Coding and Computer Science Compendium

Big O(1) - Time Complexity

Constant Time

Big O(1) - Definition

The algorithm takes the same amount of time regardless of input size.

Big O(1) - Example

Accessing an array element by index.

Big O(log n) - Time Complexity

Logarithmic Time

Big O(log n) - Definition

The time grows slowly as input size increases; usually involves cutting the problem in half repeatedly.

Big O(log n) - Example

Binary Search.

Big O(n) - Time Complexity

Linear Time

Big O(n) - Definition

The time grows directly proportional to the input size.

Big O(n) - Example

Iterating through a list (For Loop).

Big O(n log n) - Time Complexity

Linearithmic Time

Big O(n log n) - Definition

Slightly slower than linear; typical of efficient sorting algorithms.

Big O(n log n) - Example

Merge Sort, Quick Sort, Heap Sort.

Big O(n^2) - Time Complexity

Quadratic Time

Big O(n^2) - Definition

Time grows exponentially with input; performance degrades quickly.

Big O(n^2) - Example

Nested loops (Bubble Sort, Insertion Sort).

Stack - Data Structure

Last In, First Out (LIFO)

Stack - Analogy

A stack of plates; you can only take the top one off.

Stack - Key Operations

Push (add), Pop (remove), Peek (see top).

Queue - Data Structure

First In, First Out (FIFO)

Queue - Analogy

A line at a grocery store.

Queue - Key Operations

Enqueue (add), Dequeue (remove).

Hash Map / Hash Table - Data Structure

Key-Value Pair Storage

Hash Map - Efficiency

Average O(1) lookup time.

Hash Map - Concept

Uses a hash function to compute an index into an array of slots.

Binary Search Tree (BST) - Data Structure

Hierarchical Tree

BST - Rule

Left child is smaller than parent; Right child is larger than parent.

BST - Efficiency

O(log n) for search/insert/delete (if balanced).

Linked List - Data Structure

Chain of Nodes

Linked List - Concept

Elements are not stored in contiguous memory; each node points to the next.

Linked List - Pros/Cons

Fast insertion/deletion, slow access (must traverse).

HTTP 200 - Status Code

OK (Request succeeded)

HTTP 301 - Status Code

Moved Permanently (Redirect)

HTTP 400 - Status Code

Bad Request (Client error)

HTTP 401 - Status Code

Unauthorized (Authentication required)

HTTP 403 - Status Code

Forbidden (Authenticated but no permission)

HTTP 404 - Status Code

Not Found (Resource does not exist)

HTTP 500 - Status Code

Internal Server Error (Server crashed)

HTTP 502 - Status Code

Bad Gateway (Invalid response from upstream)

GET - HTTP Method

Retrieve data from a server (Idempotent).

POST - HTTP Method

Submit data to a server to create a resource.

PUT - HTTP Method

Update/Replace a resource.

DELETE - HTTP Method

Delete a resource.

Encapsulation - OOP Principle

Bundling data and methods that operate on that data within a class, hiding internal state.

Inheritance - OOP Principle

A class derives properties and behavior from a parent class.

Polymorphism - OOP Principle

Objects of different types can be treated as instances of the same class (Method Overriding/Overloading).

Abstraction - OOP Principle

Hiding complex implementation details and showing only the essential features of the object.

Recursion - Concept

A function calling itself to solve smaller instances of the problem.

Base Case - Concept

The condition that stops the recursion from looping infinitely.

chmod - Linux Command

Change file modes (permissions).

grep - Linux Command

Global Regular Expression Print (Search for text patterns).

ls - Linux Command

List directory contents.

cd - Linux Command

Change Directory.

sudo - Linux Command

SuperUser DO (Execute with admin privileges).

man - Linux Command

Manual (Display help/manual for a command).

SSH - Protocol

Secure Shell (Encrypted remote login).

Git - Tool

Distributed Version Control System.

Docker - Tool

Platform for developing, shipping, and running applications in containers.

API - Acronym

Application Programming Interface.

JSON - Acronym

JavaScript Object Notation (Data interchange format).

SQL - Acronym

Structured Query Language (Database communication).