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CodeArena – Online Technical Assessment

An online platform for running coding assessments.

Type: Full-stack · MERN
Timeline: Dec 2025 — Jan 2026
Links: Source private · demo on request

codearena.appConcept render · no public demo

CodeArenaC++ ▾

RunSubmit

Longest Increasing Subsequence

Medium

1// Longest Increasing Subsequence — O(n log n)

2int lengthOfLIS(vector<int>& nums) {

3 vector<int> tails;

4 for (int x : nums) {

5 auto it = lower_bound(tails.begin(), tails.end(), x);

6 if (it == tails.end()) tails.push_back(x);

7 else *it = x;

8 }

9 return tails.size();

10}

Test results

Case 1✓ 2 ms

Case 2✓ 1 ms

Case 3✓ 3 ms

Case 4✓ 2 ms

Case 5✓ 2 ms

Case 6✓ 4 ms

Hidden tests 12/12 passed

Runtime 4 ms · Memory 9.1 MB

● Proctoring on · Full-screen enforced · Tab switches: 0

Overview

An online platform for running coding assessments. Candidates write code in a LeetCode-style editor, each submission runs against hidden test cases, and a proctoring system watches for tab switching.

Key features

Built a LeetCode-style editor on Monaco Editor with Java, C++ and Python support.

Integrated the Judge0 API to run submissions against hidden test cases and return results straight away.

Built a proctoring system that detects tab switching and keeps the test in full-screen mode.

Built with

MongoDB
Express.js
React
Node.js
Monaco Editor
Judge0 API

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