Practice · Assess · Compete — all in one

The coding platform that runs your code for real.

Practice problems, screen candidates, and host contests on a single interface — with a real Linux sandbox underneath every submission. No rate limits, no third-party throttling.

Start practising See it in action

two_sum.pyAccepted · 41 ms

def two_sum(nums, target):
    seen = {}
    for i, n in enumerate(nums):
        need = target - n
        if need in seen:
            return [seen[need], i]
        seen[n] = i

# stdin:  2 7 11 15 / 9
# stdout: 0 1

Three modes, one platform

From a quiet evening grind to a hiring loop to a 500-person contest.

Each mode is built on the same execution engine and problem bank, so authoring once means deploying everywhere.

Practice

Sharpen against real problems.

A growing catalogue across arrays, strings, dynamic programming, graphs, and systems. Five languages out of the box. Your submission history is yours.

60+ Judge0 languages
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Assess

Screen candidates without the friction.

Compose an assessment from your bank, share one link, and watch results stream in with auto-scoring, per-test timing, and an anti-cheat session log.

Shareable invite links
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Compete

Host contests with a live leaderboard.

Time-boxed competitions with penalty-aware scoring, real-time rank updates, and registration controls. Bring your community, your university, or your team.

Real-time leaderboard
ICPC-style penalty
Open or invite-only

Problem of the day

Maximum subarray sum

Given an array of integers, return the largest possible sum of a contiguous sub-array. Kadane's algorithm earns full marks in O(n).

Mediumarraydpkadane

Solve it now

$ codenest run max-subarray.py

Input:-2 1 -3 4 -1 2 1 -5 4

Expected:6

4/4 cases · 5 ms · 4.2 MB

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