The AI-First Online Judge
for Elite Developers
Solve high-stakes challenges, get AI-powered code evaluation, and face real-time mock interviews. A rigorous gatekeeper for serious engineers.
Trusted by future engineers at
Developers Enrolled
Problems Solved
Interview Success Rate
Avg. Evaluation Time
What is SfinX OJ?
An AI-powered Online Judge with real-time interview capabilities
OJ with AI Evaluation
Our intelligent system goes beyond traditional test cases. Get comprehensive code analysis covering correctness, performance, edge-cases, and best practices.
Real-Time AI Interviews
Experience authentic interview simulations with AI acting as your interviewer. Get immediate, actionable feedback on your problem-solving approach.
How SfinX Solves Modern Assessment Problems
Built to address the shortcomings of traditional coding platforms
AI-Powered Code Evaluation
Advanced AI models analyze your code for correctness, efficiency, and best practices.
Intelligent Test Generation
Automatically generated edge cases that thoroughly test your solution's robustness.
Performance Analysis
Deep analysis of time complexity, space usage, and handling of boundary conditions.
Plagiarism Detection
Sophisticated detection systems ensure the integrity of every submission.
Real-Time Mock Interviews
Live interview simulations with structured feedback to prepare for actual interviews.
How it works
From sign-up to FAANG-ready
Three steps. No fluff.
Create your account
Sign up free. No credit card needed. Unlock the full problem archive and your personal performance dashboard instantly.
Solve real challenges
Pick a problem, write your solution in your language of choice, and submit. Our AI evaluates it in under 2 seconds.
Get evaluated & improve
Receive detailed feedback on correctness, efficiency, edge cases, and code style. Track your progress and identify gaps over time.
Developer-Focused Documentation
Everything you need to understand the platform, structured for developers by developers.
Clear & Structured Docs
Comprehensive documentation organized for quick reference and deep dives.
Problem Formats
Detailed specifications for input/output formats and constraints.
Submission Rules
Clear guidelines on code requirements, time limits, and memory constraints.
Evaluation Methodology
Transparent explanation of how submissions are scored and evaluated.
API References
Complete API documentation for integrations and automated submissions.
# AI-Powered Two Sum Solution
def two_sum(nums: list[int], target: int) -> list[int]:
"""
Find two numbers that add up to target.
Time Complexity: O(n)
Space Complexity: O(n)
"""
seen = {}
for i, num in enumerate(nums):
complement = target - num
if complement in seen:
return [seen[complement], i]
seen[num] = i
return []
# ✓ All 847 test cases passed
# ✓ Edge cases: handledSimple, Transparent Pricing
Choose the plan that fits your needs. No hidden fees.
Free
For developers just getting started
- Unlimited practice problems
- Basic code evaluation
- 2 AI Interviews per month
- Community support
- Limited performance insights
Plus
Everything you need to get interview-ready
- Unlimited practice problems
- Unlimited AI Interviews
- Advanced AI-powered evaluation
- Detailed interview feedback
- Mock interviews
- Performance analytics
- Priority support
Pro
For power users who want elite preparation
- Everything in Plus
- Deep performance breakdowns
- Faster evaluations
- Early access to new features
- Advanced analytics & insights
- Dedicated support
The comparison
SfinX vs Traditional
See the difference at a glance
Intelligent analysis beyond pass/fail
Comprehensive boundary testing
Live 1:1 sessions with AI interviewer
Evaluation results under 2 seconds
Actionable style and idiomatic feedback
Time and space complexity breakdown
Protects integrity of assessments
Broad library of practice problems
Not available
Not available
Not available
10–30 seconds
Not available
Basic only
Limited
Available
Evaluation Speed Comparison
What developers say
Developers who made it
Real feedback from engineers who used SfinX to land their next role.
SfinX's AI feedback caught an edge case I'd been ignoring for months. The explanation was clearer than anything I'd read in documentation. Passed my Google L5 interview on the first try.
Alex T.
Senior Software Engineer · Google
Unlike LeetCode, the AI actually explains *why* my solution is slow — not just that it is. That shift in feedback quality completely changed how I approach optimization problems.
Priya M.
Software Engineer · Meta
The mock interviews are shockingly realistic. I went into my Stripe interview nervous and came out confident because I had already practiced under the same pressure. Worth every cent.
James K.
Software Engineer · Stripe
Common questions
Frequently asked
Straight answers to questions we hear most.
Built by engineers who've been there
We've sat through the same grueling technical interviews, wrestled with vague feedback from traditional judges, and wondered if our code was actually good — or just passing test cases.
SfinX is the platform we needed. We're building it in the open.
Free to start
Ready to test what you're actually made of?
Join 2,400+ developers already using SfinX. No credit card needed.