Master Code, Facts & everything in between.
CodeNFacts is your launchpad for Programming, DSA, AI/ML, and Data Science with hands-on internships, real projects, and an AI tutor that never sleeps.
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AI Engineering Track
What is coding,
really?
Coding is writing instructions a computer can follow, exactly and in order, to make something happen. This page breaks down what coding actually is, then walks through the pipeline that runs every time you hit "Run."
What is coding?
It's a language
Written in Python, JavaScript, or similar - each with strict vocabulary and grammar, built to leave nothing open to interpretation.
It's a recipe
A precise sequence of steps: take input, transform it, produce a result. Reorder a step and the outcome changes.
It's for a machine
No room for guessing. A computer runs exactly what's written - which is why one misplaced character can matter.
What happens when you code?
Hitting "Run" starts a short, exact pipeline. Here's what happens between your keystrokes and the result on screen.
You write code
hello.pyInstructions typed in a human-readable language - Python, JavaScript, whatever the job calls for.
The file is saved
→ diskYour editor stores it as plain text. Still just words - nothing has run yet.
It gets translated
compiler / interpreterA compiler or interpreter reads your code and converts it toward something the machine can act on.
Machine code appears
01001000 01101001Your program becomes binary - the only dialect a processor natively executes.
The CPU executes it
cpu.exec()The processor works through each instruction in order, billions of times a second.
Output appears
> Hello, world!The result surfaces as text, pixels, sound, or motion - whatever you told it to produce.
Want to learn from AI?
Pick a roadmap, drill into a topic, and ask a real question - your tutor breaks it down step by step, live.
ai-tutor --init
Hey! Pick a roadmap on the left, expand a topic, and tap any question - or just type your own below.
Master DSA Topics
Every data structure & algorithm topic you need - from arrays to advanced graph theory - organized into one trackable roadmap.
- Time & Space Complexity (Big-O)Easy
- Recursion & Backtracking BasicsMedium
- Bit ManipulationMedium
- Number Theory (GCD, Primes, Sieve)Medium
- Modular ArithmeticEasy
All Coding Problems
3,200+ coding interview style problems. Search, filter by difficulty, topics & companies.
Showing 1-20 of 3,200 problems
Add Two Numbers
Find the optimal solution using dynamic programming techniques.
Longest Substring Without Repeating Characters
Given an array of integers, solve the classic problem efficiently.
Median of Two Sorted Arrays
Greedy approach yields the optimal result for this problem.
Longest Palindromic Substring
Use bit manipulation to solve this problem in constant space.
Zigzag Conversion
Solve this graph traversal problem using BFS or DFS.
Reverse Integer
Greedy approach yields the optimal result for this problem.
String to Integer (atoi)
Given an array of integers, solve the classic problem efficiently.
Palindrome Number
Use two pointers or sliding window to achieve linear time.
Regular Expression Matching
Combine multiple data structures to support the required operations.
Container With Most Water
Backtracking is needed to explore all valid combinations.
Integer to Roman
Handle edge cases carefully while processing the linked list.
Roman to Integer
Combine multiple data structures to support the required operations.
Longest Common Prefix
Combine multiple data structures to support the required operations.
3Sum
Solve this graph traversal problem using BFS or DFS.
3Sum Closest
Combine multiple data structures to support the required operations.
Letter Combinations of a Phone Number
Prefix sums or cumulative techniques simplify the calculation.
4Sum
Implement a solution with optimal time and space complexity.
Remove Nth Node From End of List
Use bit manipulation to solve this problem in constant space.
Valid Parentheses
Greedy approach yields the optimal result for this problem.
Merge Two Sorted Lists
Greedy approach yields the optimal result for this problem.
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Start coding in seconds
Pick a language below - your editor opens instantly.
Tutorials Library
Pick a topic to open its dedicated tutorial page.
Prerequisites
What to know before you start coding seriously.
DSA
Data structures & algorithms, from arrays to graphs.
Practice Questions
Curated problems to drill every concept.
Python
Readable, versatile, and everywhere in AI/ML.
Java
OOP fundamentals and enterprise-grade backend skills.
C++
Performance, STL, and competitive programming staples.
Road Map
A step-by-step path from beginner to job-ready.
Artificial Intelligence (AI)
The big picture: what AI is and how it actually works.
Machine Learning
Algorithms that learn patterns from data.
Data Science
Turning raw data into decisions.
SQL
Querying and managing relational data.
Web Dev
Full-stack skills to ship real products.
Git
Version control that every developer must master.
Interview Questions
Real questions asked at top tech companies.
Projects
Build real things to put on your resume.
Resume Tips
Get past the ATS and into the interview room.
Aptitude
Quant, logical reasoning, and verbal prep for tests.
Quizzes
Test what you've learned, topic by topic.
The Developer’s Toolbox
Compilers, AI assistance, utilities, and learning resources - every tool on CodeNFacts, organized so you spend less time searching and more time building.
HTML Editor
Write and preview HTML, CSS & JS live, right in the browser.
Python Compiler
Run Python scripts instantly with no installs or setup.
Java Compiler
Compile and run Java programs straight from your browser.
C Compiler
Test C programs fast with an in-browser GCC sandbox.
AI Code Tutor
Get unstuck with an AI that explains errors and reviews your code.
DSA Visualizer
Watch sorting, trees & graphs animate step by step.
Regex Tester
Build and debug regular expressions with live match highlighting.
JSON Formatter
Format, validate, and minify JSON in a single click.
API Request Tester
Send GET/POST requests and inspect responses without leaving the site.
Snippet Library
Searchable, copy-ready snippets for every language you're learning.
Git Cheat Sheet
Every Git command you'll actually use, organized by workflow.
Learning Roadmaps
Structured paths for DSA, Web Dev, and AI/ML — start to finish.
Learn Better Together
Connect with learners, collaborate on projects, discuss ideas, participate in coding challenges, and grow alongside a community that shares your passion for technology.
Meet Developers
Build meaningful connections with developers, students, mentors, and creators from around the world.
Share Knowledge
Ask questions, answer discussions, exchange resources, and learn from real experiences shared by the community.
Grow Together
Participate in coding events, collaborate on projects, and stay motivated through an active learning ecosystem.
Choose Your Learning Roadmap
Every roadmap is carefully structured to take you from beginner fundamentals to real-world projects, helping you build practical skills step by step.
Data Structures & Algorithms
Master problem solving with arrays, trees, graphs and dynamic programming.
View RoadmapArtificial Intelligence
Explore Machine Learning, Deep Learning, LLMs and practical AI projects.
View RoadmapLearn with Confidence
Whether you're starting your programming journey or preparing for technical interviews, our structured learning paths help you stay focused and build real skills.
Explore Roadmaps