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Learn it. See it run. Prove you can code it.

Ask. Think. Code. Get judged. Remember forever.

A practice workspace where the tutor asks questions instead of handing over answers, and everything you learn is scheduled back to you for review.

  • Socratic AI tutor that guides your logic without spoiling the solution

  • Interactive visual steppers for 17 complex algorithms & data structures

  • 188+ offline DevDocs cheat sheets for Python, Java, C++, TypeScript, and Go

  • 2,078 compiler-judged challenges with instant test verification

guest@codementor: ~ — bash
Last login: Wed Feb 25 18:42:10 2026 on ttys000
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CodeMentor AI v2.4.0 — free Socratic mentor · visual algorithms · DevDocs
2078+ judged problems · 17 visualizers · 188+ docs · 100% free, open source
Type 'help' for commands — or poke the filesystem: ls, cat README.md, neofetch
guest@codementor:~$
● bash
12:00:00
Try CLI:
2,078+

Judged problems →

5 Languages

Python · JS · Java · C++ · Go

17 Steppers

Interactive visualizers →

188+

Standard library docs →

Try it. Right here.

Simulations, quizzes, code runner, side-by-side diffs — all live below.

Interactive Bubble Sort Simulation

Click 'Next Step' or press 'Play' to watch comparisons and array swaps in real time.

17
[0]
42
[1]
89
[2]
23
[3]
56
[4]
12
[5]
Step 1/21: Comparing 42 and 17: out of order — swapped.

Step the sort. Break the code. Keep the memory.

Every tool below runs in your browser. No account, no setup.

01 / visualizers

Watch algorithms think.

17 simulations — sorting, graphs, DP, heaps. Step forward, back, or scrub the speed. Every click is a real comparison.

17 simulations·step / pause / speed·live variable trace
Open visualizers
Step 1/31
42
[0]mid
17
[1]mid
89
[2]mid
23
[3]mid
56
[4]mid
12
[5]mid
Comparing Sorted
Generic PseudocodeLine 1 active
1function bubbleSort(arr, n):▶ RUNNING
2 for i from 0 to n - 1:
3 for j from 0 to n - i - 2:
4 if arr[j] > arr[j + 1]:
5 swap(arr[j], arr[j + 1])
6 return arr
Active Variable State
n:6i:-j:-action:initialize
Initialize: bubble sort starts with unsorted array of size 6.
example

Daily challenge

One problem a day, and it feeds your spaced review queue. Needs a free account.

Today's challenge

practice arena

Judged, not graded.

12–15 hidden tests. Strict time and memory limits. No hand-waving.

solution.pyTwo Pointers · O(N) Time
def twoSum(numbers: list[int], target: int) -> list[int]:
    left, right = 0, len(numbers) - 1
    while left < right:
        current_sum = numbers[left] + numbers[right]
        if current_sum == target:
            return [left + 1, right + 1]
        elif current_sum < target:
            left += 1
        else:
            right -= 1
    return []
Static sample verdict — press Reveal, then run live code inside Practice.
Runtime0.38s
TimeO(N)
MemoryO(1)

Input: numbers = [2, 7, 11, 15], target = 9

Output: [1, 2](0.02ms)

2,078 problems
12–15 Hidden Cases

Tuned for worst-case asymptotics, corner inputs, and stack limits.

5 Native Compilers

Real execution: in-browser Pyodide plus Judge0 CE fallback across Python, JavaScript, Java, C++, and Go.

XP Hint Ladder

3-tier Socratic nudges that recover XP upon clean solution submission.

Structured curricula

Syntax → Data Structures → Algorithms → Interview-ready.

Data Structures & Algorithms

Arrays, trees, graphs, sorting, and dynamic programming: the core of most technical interviews.

Topics Covered
Arrays & Strings
Linked Lists
Stacks & Queues
Hash Tables
Binary Trees
Binary Search Trees
Heaps
Graphs
Sorting Algorithms
Searching Algorithms
Recursion
Dynamic Programming
Greedy Algorithms
Backtracking

Frequently asked questions

Short answers to the things people ask most.

Not to look around. As a guest you can read every practice problem, step through the algorithm visualizers, browse DevDocs, and keep notes. Running and submitting code, AI hints, the daily challenge, and your streak and XP need a free account.

Why I built this

Built for developers who learn by doing, not watching.

Why it exists

One screen instead of four tabs.

The tutorial trap

Watching video solutions feels like progress, until you face a blank editor and your mind freezes.

The Socratic approach

The tutor works out where your logic breaks and asks guiding questions, so you find the answer yourself.

I built CodeMentor AI because I kept bouncing between videos, a judge, docs, and a chatbot, and forgetting it all by Monday. The visual stepper, the compiler, the reference docs, and the Socratic tutor now live in one workspace, wired to the same spaced-repetition queue.

Hints before answers
Runs in your browser
Free and open source
The Creator
mrinall.dev
Mrinall Samal
Founder & Lead Engineer

Have ideas, feedback, or a feature request? Reach out directly — every message shapes the next version:

Visit mrinall.devSend an Email

Tutorials lie. Compilers don't.

2,078 problems. 17 visual steppers. 188+ docs. All free.