Introduction to the LeetCode System

Design a coding judge that accepts submissions quickly, runs untrusted programs within limits, and records results that can be reproduced under a known problem and runtime version.

Introduction

LeetCode is a useful reference for a coding-practice and contest platform. In our design, each problem combines a statement, constraints, test data, and a judging rule. A submission is evaluated against a specific version of that problem and a specific compiler or runtime configuration.

The platform has two different workloads: serving ordinary web requests and executing submitted code. The second needs isolated workers, resource budgets, and recoverable job state. Correctness checks can be reproducible under controlled inputs, but arbitrary programs and measured runtimes are not inherently deterministic. Keep grading policy separate from performance noise and infrastructure failures.

The following illustration shows the high-level workflow of a LeetCode-style system from problem selection to evaluation: