TraceCodeWatch your solutions come alive.
Master algorithms by seeing them work. Write solutions to coding problems and trace every variable, pointer, and state change live from your code.
PythonHow it works
You learn a pattern, practice it on a real problem, then test yourself in a timed interview.
Learn how each pattern works
Each lesson focuses on a single pattern. You learn how to recognize it, how the technique works, and the common mistakes to avoid.
Explore lessonsTraverse a tree level by level using a queue, processing all nodes at each depth before moving deeper.
Predict each step before you see it
Each problem becomes a series of small questions. You answer each one before the engine shows the next step.
Try a problemWhat should the waiting frontier contain?
Node 3 has been processed. Its children 9 and 20 have been discovered, while nodes 15 and 7 have not been reached yet.
Take a timed mock interview
Timed assessments built on realistic, company-style problems. Your code runs against hidden tests, and you get feedback after each session.
Start a mock assessmentChoose your plan
Free
Everything you need to learn by seeing.
Get started- Step-through visualizer for arrays, trees, graphs, stacks & heaps
- Run your code in Python, JavaScript, C++, Java & C#
- Practice problems & guided walkthroughs
- Progress tracking across every problem
Pro
Billed monthly
Understand faster. Share what you build.
Everything in Free, plus
- Step-by-step explanations for every line — in plain English
- Export trace videos & GIFs to share anywhere
- Cloud judging for your solutions
- Sync your work across all your devices
Cancel anytime · No card required to start on Free
Ready to level up your coding skills?
Join engineers who use TraceCode to think deeper, trace faster, and practice with intent.