[Backend] - Lu Chi Tam (Mat Lu)

src/problem4/index.ts

@@ -0,0 +1,24 @@
+// The complexity of this function is O(n) because it iterates through all numbers from 0 to n once.
+// The efficiency of this function is not optimal for large values of n, as it requires n iterations to compute the sum.
+// n is <= Math.MAX_SAFE_INTEGER, so we can safely compute the sum without worrying about overflow in JavaScript.
+function sum_to_n_a(n: number): number {
+  let count = 0
+  for (let i = 0; i <= n; i++) {
+    count += i
+  }
+  return count
+}
+
+// The complexity of this function is O(1) because it uses a constant number of operations to compute the sum, regardless of the value of n.
+// The efficiency of this function is optimal for all values of n, as it computes the sum in constant time.
+// n is <= Math.MAX_SAFE_INTEGER, so we can safely compute the sum without worrying about overflow in JavaScript.
+function sum_to_n_b(n: number): number {
+  return (n * (n + 1)) / 2
+}
+
+// The complexity of this function is O(n) because it iterates through all numbers from 1 to n once using recursion.
+// The efficiency of this function is not optimal for large values of n, as it requires n iterations to compute the sum.
+// n is <= Math.MAX_SAFE_INTEGER, so we can safely compute the sum without worrying about overflow in JavaScript.
+function sum_to_n_c(n: number): number {
+  return n === 0 ? 0 : n + sum_to_n_c(n - 1)
+}

src/problem5/express-ts/.gitignore

@@ -0,0 +1,5 @@
+
+
+
+.env
+node_modules/

src/problem5/express-ts/README.md

@@ -0,0 +1,156 @@
+# Express TypeScript Product API
+
+A simple REST API built with Express, TypeScript, and MongoDB (Mongoose) for managing products.
+
+## Features
+
+- Health check endpoint
+- Create, read, update, and delete products
+- List products with pagination and optional filters
+- MongoDB connection via environment variables
+
+## Tech Stack
+
+- Node.js
+- Express
+- TypeScript
+- Mongoose
+- dotenv
+
+## Project Structure
+
+```text
+src/
+  index.ts                 # app entrypoint
+  configs/
+    index.ts               # config initializer
+    mongodb.ts             # MongoDB connection
+  controllers/
+    product.controller.ts  # product handlers
+  models/
+    products.model.ts      # product schema/model
+  routes/
+    index.ts               # base router
+    product.route.ts       # product routes
+```
+
+## Prerequisites
+
+- Node.js 18+
+- npm or yarn
+- A MongoDB instance (local or cloud)
+
+## Environment Variables
+
+Create a `.env` file in the project root:
+
+```env
+MONGO_URI=mongodb://localhost:27017
+MONGO_DB=your_database_name
+```
+
+## Installation
+
+Using npm:
+
+```bash
+npm install
+```
+
+Using yarn:
+
+```bash
+yarn install
+```
+
+## Run the App
+
+Development mode (with auto-reload):
+
+```bash
+npm run dev
+```
+
+Start mode:
+
+```bash
+npm start
+```
+
+The server runs on:
+
+```text
+http://localhost:3000
+```
+
+## API Endpoints
+
+Base path: `/api`
+
+### Health Check
+
+- `GET /healthcheck`
+
+Response:
+
+```json
+{ "status": "ok" }
+```
+
+### Create Product
+
+- `POST /api/product`
+
+Request body:
+
+```json
+{
+  "name": "Keyboard",
+  "price": 49.99,
+  "description": "Mechanical keyboard"
+}
+```
+
+### Get Product by ID
+
+- `GET /api/product/:id`
+
+### Update Product
+
+- `PUT /api/product/:id`
+
+Request body (any updatable fields):
+
+```json
+{
+  "name": "Keyboard Pro",
+  "price": 79.99,
+  "description": "Updated description"
+}
+```
+
+### Delete Product
+
+- `DELETE /api/product/:id`
+
+### Get All Products
+
+- `GET /api/products`
+
+Optional query params:
+
+- `page` (default: `1`)
+- `limit` (default: `10`)
+- `name` (case-insensitive partial match)
+- `price` (exact number match)
+
+Example:
+
+```http
+GET /api/products?page=1&limit=5&name=key&price=49.99
+```
+
+## Notes
+
+- If `MONGO_URI` or `MONGO_DB` is missing, the app will throw an error during startup.
+- JSON request parsing is enabled globally.

src/problem5/express-ts/package.json

@@ -0,0 +1,23 @@
+{
+  "name": "express-ts",
+  "version": "1.0.0",
+  "main": "index.js",
+  "license": "MIT",
+  "dependencies": {
+    "dotenv": "^17.4.1",
+    "express": "^5.2.1",
+    "mongoose": "^9.4.1"
+  },
+  "devDependencies": {
+    "@types/express": "^5.0.6",
+    "@types/node": "^25.6.0",
+    "nodemon": "^3.1.14",
+    "ts-node": "^10.9.2",
+    "typescript": "^6.0.2"
+  },
+  "scripts": {
+    "start": "ts-node src/index.ts",
+    "dev": "nodemon --watch 'src/**/*.ts' --exec 'ts-node' src/index.ts"
+  },
+  "type": "commonjs"
+}

src/problem5/express-ts/src/configs/index.ts

@@ -0,0 +1,11 @@
+import { connectToMongoDB } from './mongodb'
+
+export const initConfigs = async () => {
+  try {
+    await connectToMongoDB()
+    console.log('All configurations initialized successfully')
+  } catch (error) {
+    console.error('Error initializing configurations:', error)
+    throw error
+  }
+}

src/problem5/express-ts/src/configs/mongodb.ts

@@ -0,0 +1,20 @@
+import { connect } from 'mongoose'
+
+export const connectToMongoDB = async () => {
+  try {
+    const mongoUri = process.env['MONGO_URI']
+    const dbName = process.env['MONGO_DB']
+    if (!mongoUri || !dbName) {
+      throw new Error(
+        'MONGO_URI and MONGO_DB must be defined in environment variables'
+      )
+    }
+    await connect(mongoUri, {
+      dbName: dbName
+    })
+    console.log('Connected to MongoDB')
+  } catch (error) {
+    console.error('Error connecting to MongoDB:', error)
+    throw error
+  }
+}

src/problem5/express-ts/src/controllers/product.controller.ts

@@ -0,0 +1,107 @@
+import { Request, Response } from 'express'
+import Product from '../models/products.model'
+
+export const createProduct = async (req: Request, res: Response) => {
+  try {
+    const { name, price, description } = req.body as {
+      name: string
+      price: number
+      description?: string
+    }
+
+    if (!name || !price) {
+      return res.status(400).json({ error: 'Name and price are required' })
+    }
+
+    const product = new Product({ name, price, description })
+    await product.save()
+    return res.status(201).json({
+      status: 'success',
+      message: 'Product created successfully'
+    })
+  } catch (error: any) {
+    return res.status(400).json({ error: error.message })
+  }
+}
+
+export const getProducts = async (req: Request, res: Response) => {
+  try {
+    const {
+      page = 1,
+      limit = 10,
+      name,
+      price
+    } = req.query as {
+      page?: string
+      limit?: string
+      name?: string
+      price?: string
+    }
+    const products = await Product.find({
+      ...(name && { name: { $regex: name, $options: 'i' } }),
+      ...(price && { price: Number(price) })
+    })
+      .skip((Number(page) - 1) * Number(limit))
+      .limit(Number(limit))
+    return res.status(200).json({
+      status: 'success',
+      data: products
+    })
+  } catch (error: any) {
+    return res.status(400).json({ error: error.message })
+  }
+}
+
+export const getProductById = async (req: Request, res: Response) => {
+  try {
+    const { id } = req.params
+    const product = await Product.findById(id)
+    if (!product) {
+      return res.status(404).json({ error: 'Product not found' })
+    }
+    return res.status(200).json({
+      status: 'success',
+      data: product
+    })
+  } catch (error: any) {
+    return res.status(400).json({ error: error.message })
+  }
+}
+
+export const updateProduct = async (req: Request, res: Response) => {
+  try {
+    const { id } = req.params
+    const { name, price, description } = req.body
+    const product = await Product.findByIdAndUpdate(
+      id,
+      { name, price, description },
+      { new: true }
+    )
+    if (!product) {
+      return res.status(404).json({ error: 'Product not found' })
+    }
+    return res.status(200).json({
+      status: 'success',
+      message: 'Product updated successfully',
+      data: product
+    })
+  } catch (error: any) {
+    return res.status(400).json({ error: error.message })
+  }
+}
+
+export const deleteProduct = async (req: Request, res: Response) => {
+  try {
+    const { id } = req.params
+    const product = await Product.findByIdAndDelete(id)
+    if (!product) {
+      return res.status(404).json({ error: 'Product not found' })
+    }
+    return res.status(200).json({
+      status: 'success',
+      message: 'Product deleted successfully'
+    })
+  } catch (error: any) {
+    return res.status(400).json({ error: error.message })
+  }
+}

src/problem5/express-ts/src/index.ts

@@ -0,0 +1,29 @@
+import express from 'express'
+import type { Application, Request, Response } from 'express'
+import { initConfigs } from './configs'
+import dotenv from 'dotenv'
+import routes from './routes'
+
+dotenv.config({
+  debug: true,
+  override: true,
+  encoding: 'utf8'
+})
+
+const port = 3000
+const app: Application = express()
+
+app.use(express.json({ strict: false }))
+app.use(express.urlencoded({ extended: false }))
+
+initConfigs()
+
+app.get('/healthcheck', (_: Request, res: Response) => {
+  res.status(200).json({ status: 'ok' })
+})
+
+app.use(routes)
+
+app.listen(port, () => {
+  console.log(`Server running at http://localhost:${port}`)
+})

src/problem5/express-ts/src/models/products.model.ts

@@ -0,0 +1,10 @@
+import { model, Schema } from 'mongoose'
+
+const productSchema = new Schema({
+  name: { type: String, required: true },
+  price: { type: Number, required: true },
+  description: { type: String }
+})
+
+const Product = model('Product', productSchema)
+export default Product