I Solved 800+ LeetCode Problems in C# - Here's What I Built

Sivalingam — Mon, 30 Mar 2026 18:04:24 +0000

What's on the site

Every solution page has:

✅ Clean, readable C# code with syntax highlighting
📝 The approach explained in plain English
⏱️ Time and space complexity
🔗 Direct link to the LeetCode problem

You can browse by topic (Dynamic Programming, Trees, Graphs, Sliding Window, Two Pointers, and 40+ more) or filter by difficulty (Easy / Medium / Hard).

Example — Two Sum

Here's what a typical solution looks like:

// Approach: Use a dictionary to store each number's index.
// For each number, check if its complement (target - num) already exists.
// Time: O(n) Space: O(n)

public class Solution {
    public int[] TwoSum(int[] nums, int target) {
        var map = new Dictionary<int, int>();
        for (int i = 0; i < nums.Length; i++) {
            int complement = target - nums[i];
            if (map.ContainsKey(complement))
                return new int[] { map[complement], i };
            map[nums[i]] = i;
        }
        return Array.Empty<int>();
    }
}

Every solution follows this pattern — the comment at the top explains the core idea before you read any code.

Why C#?

C# is underused in competitive programming, but it's a great choice:

Strong typing catches bugs the compiler
LINQ makes array/list operations expressive
Dictionary<K,V> and HashSet<T> are fast and easy to use
It's what most .NET/backend engineers use day-to-day

If you're preparing for interviews at Microsoft, Amazon, or any .NET shop, practicing in C# makes your prep directly transferable.

GeeksforGeeks too

I also solve the GFG Problem of the Day every day in Java. Those are at dsasolved.com/gfg — 530+ solutions and growing daily.

Tech behind the site

Built with Next.js 14 (App Router), fully statically generated — 1,380+ pages pre-rendered at build time. Uses Shiki for syntax highlighting. Deployed on Vercel.

The solutions themselves live in a GitHub repo: each .cs file is one problem. The site reads them at build time and generates the pages.

I built a linter that enforces Clean Architecture rules in TypeScript

Sivalingam — Wed, 11 Mar 2026 19:13:21 +0000

The problem

In every TypeScript codebase I've worked on, the same violation appears eventually:

// controllers/orderController.ts
import { OrderRepository } from '../repositories/orderRepository'; // ❌

A controller importing a repository directly. The service layer completely bypassed.

ESLint can't catch this - it has no concept of architectural layers. Code reviews catch it sometimes, but not always. And the bugs it causes are subtle.

So I built architecture-linter.

How it works

You create a .context.yml in your project root:

architecture:
  layers:
    - controller
    - service
    - repository

rules:
  controller:
    cannot_import:
      - repository

Then run:

npx architecture-linter scan

Output:

❌ Architecture violation detected

   File:   controllers/orderController.ts
   Import: repositories/orderRepository
   Rule:   Controller cannot import Repository

Found 1 violation in 3 file(s) scanned.

Setup takes 2 minutes

npm install --save-dev architecture-linter
npx architecture-linter init   # auto-detects your framework and layers
npx architecture-linter scan

init automatically detects NestJS and Next.js from your package.json and generates the right config - including file-suffix scanning (.controller.ts, .service.ts, etc.) for NestJS projects. Pass --force to overwrite an existing config.

Three ways to use it

1. CLI - run locally or in any CI pipeline

2. VS Code extension - violations appear as red squiggles in real time, with fix hints in the Problems panel

3. GitHub Action - annotates PRs with inline violations on the exact line

- uses: cvalingam/architecture-linter@v1
  with:
    token: ${{ secrets.GITHUB_TOKEN }}

Built-in presets

No need to write rules from scratch. Use a preset:

extends: nestjs   # or clean-architecture, hexagonal, nextjs

Available presets: nestjs, clean-architecture, hexagonal, nextjs

DEV Community: Sivalingam