[FE]: Code challenge solution - Dao Minh Duc

readme.md

@@ -1,10 +1,46 @@
-# 99Tech Code Challenge #1 #
+# 99Tech Code Challenge #1
 
 Note that if you fork this repository, your responses may be publicly linked to this repo.  
-Please submit your application along with the solutions attached or linked.   
+Please submit your application along with the solutions attached or linked.
 
 It is important that you minimally attempt the problems, even if you do not arrive at a working solution.
 
-## Submission ##
+## Submission
+
 You can either provide a link to an online repository, attach the solution in your application, or whichever method you prefer.
 We're cool as long as we can view your solution without any pain.
+
+## Problem Descriptions
+
+### Problem 1
+In `src/problem1/index.js` you’ll find three implementations of the same algorithm – summing the first `n` natural numbers:
+
+- **`sum_to_n_a`**: straightforward iterative loop accumulating the sum.
+- **`sum_to_n_b`**: recursive version that adds `n` to the result of `sum_to_n_b(n-1)` (note the stack‑overflow warning for large `n`).
+- **`sum_to_n_c`**: constant‑time formula using `n * (n + 1) / 2`.
+
+Each variant demonstrates a different approach to solving the same mathematical problem and could be used to discuss performance and edge cases.
+
+### Problem 2
+This directory contains a working Vite‑powered React + TypeScript project, not just a boilerplate.  Key points:
+
+- **Configuration**: `tsconfig.json`, `tsconfig.node.json`, `.eslintrc.cjs`, and `vite.config.ts` are already set up for linting, type checking, and hot‑module reloading.
+- **Dependencies** include `react`, `react-dom`, `axios`, `styled-components` along with TypeScript and ESLint tooling.
+- **Structure**: under `src/` you’ll find a small swap‑UI application:
+  - Reusable components (`Button`, `Loading`, `TokenImage`, `SwapSection`, `SelectTokensModal`, `ConfirmSwapModal`)
+  - Pages (`SwapPage`) and styling helpers (`Flex.styled.ts`)
+  - Shared `constants`, `enums`, `types`, and utility scripts (e.g. `generateImportImages.js`)
+  - Asset management under `assets/img` with an importer script
+- **Scripts**: `npm run dev` starts the dev server, `npm run build` compiles TypeScript and bundles via Vite, and there’s a helper `generateImageObject` script.
+
+The application demonstrates a typical modern React stack with styled‑components and structured folder layout.
+
+### Problem 3
+Two versions of a wallet balance page are provided:
+
+- **`Example.tsx`** – an initial implementation sketching out the component, priority logic, and a placeholder `Datasource` class.
+- **`RefactorVersion.tsx`** – a refactored, more polished variant that adds type definitions, `makeStyles` for styling, and detailed comments about performance considerations.
+
+Both versions use a custom hook `useWalletBalances` (imported but not shown) to retrieve balances, then fetch price data from `https://interview.switcheo.com/prices.json` via the `Datasource` class. Balances are filtered and sorted by blockchain priority and converted to `WalletRow` elements with formatted amounts and USD values. The refactor includes notes about memoization, avoiding redundant calculations, and key generation for list items.
+
+This problem exercises React hooks, async data fetching, and basic optimization/documentation practices.

src/problem1/index.js

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+// Implementation 1: Iterative
+// This implementation uses a simple iterative loop to calculate the summation.
+function sum_to_n_a(n) {
+    let sum = 0;
+
+    for (let i = 1; i <= n; i++) {
+        sum += i;
+    }
+
+    return sum;
+}
+
+// Implementation 2: Recursive
+// This implementation uses recursion to calculate the summation.
+//Warning: When n is large, this implementation may cause a stack overflow error due to the large number of recursive calls.
+function sum_to_n_b(n) {
+    if (n === 1) {
+        return 1;
+    } else {
+        return n + sum_to_n_b(n - 1);
+    }
+}
+
+// Implementation 3: Formula
+// This implementation utilizes the formula for the summation of the first N natural numbers, which is n * (n + 1) / 2.
+function sum_to_n_c(n) {
+    return (n * (n + 1)) / 2;
+}

src/problem2/.eslintrc.cjs

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+module.exports = {
+  root: true,
+  env: { browser: true, es2020: true },
+  extends: [
+    'eslint:recommended',
+    'plugin:@typescript-eslint/recommended',
+    'plugin:react-hooks/recommended',
+  ],
+  ignorePatterns: ['dist', '.eslintrc.cjs'],
+  parser: '@typescript-eslint/parser',
+  plugins: ['react-refresh'],
+  rules: {
+    'react-refresh/only-export-components': [
+      'warn',
+      { allowConstantExport: true },
+    ],
+  },
+}

src/problem2/.gitignore

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+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+lerna-debug.log*
+
+node_modules
+dist
+dist-ssr
+*.local
+
+# Editor directories and files
+.vscode/*
+!.vscode/extensions.json
+.idea
+.DS_Store
+*.suo
+*.ntvs*
+*.njsproj
+*.sln
+*.sw?

src/problem2/README.md

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+# React + TypeScript + Vite
+
+This template provides a minimal setup to get React working in Vite with HMR and some ESLint rules.
+
+Currently, two official plugins are available:
+
+- [@vitejs/plugin-react](https://github.com/vitejs/vite-plugin-react/blob/main/packages/plugin-react/README.md) uses [Babel](https://babeljs.io/) for Fast Refresh
+- [@vitejs/plugin-react-swc](https://github.com/vitejs/vite-plugin-react-swc) uses [SWC](https://swc.rs/) for Fast Refresh
+
+## Expanding the ESLint configuration
+
+If you are developing a production application, we recommend updating the configuration to enable type aware lint rules:
+
+- Configure the top-level `parserOptions` property like this:
+
+```js
+export default {
+  // other rules...
+  parserOptions: {
+    ecmaVersion: 'latest',
+    sourceType: 'module',
+    project: ['./tsconfig.json', './tsconfig.node.json'],
+    tsconfigRootDir: __dirname,
+  },
+}
+```
+
+- Replace `plugin:@typescript-eslint/recommended` to `plugin:@typescript-eslint/recommended-type-checked` or `plugin:@typescript-eslint/strict-type-checked`
+- Optionally add `plugin:@typescript-eslint/stylistic-type-checked`
+- Install [eslint-plugin-react](https://github.com/jsx-eslint/eslint-plugin-react) and add `plugin:react/recommended` & `plugin:react/jsx-runtime` to the `extends` list

src/problem2/index.html

@@ -1,27 +1,13 @@
-<html>
-
-<head>
-  <meta name="viewport" content="width=device-width, initial-scale=1">
-  <title>Fancy Form</title>
-
-  <!-- You may add more stuff here -->
-  <link href="style.css" rel="stylesheet" />
-</head>
-
-<body>
-
-  <!-- You may reorganise the whole HTML, as long as your form achieves the same effect. -->
-  <form onsubmit="return !1">
-    <h5>Swap</h5>
-    <label for="input-amount">Amount to send</label>
-    <input id="input-amount" />
-
-    <label for="output-amount">Amount to receive</label>
-    <input id="output-amount" />
-
-    <button>CONFIRM SWAP</button>
-  </form>
-  <script src="script.js"></script>
-</body>
-
+<!DOCTYPE html>
+<html lang="en">
+    <head>
+        <meta charset="UTF-8" />
+        <link rel="icon" type="image/svg+xml" href="/vite.svg" />
+        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+        <title>Fancy Swap Form</title>
+    </head>
+    <body>
+        <div id="root"></div>
+        <script type="module" src="/src/main.tsx"></script>
+    </body>
 </html>

src/problem2/package.json

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+{
+    "name": "problem2",
+    "private": true,
+    "version": "0.0.0",
+    "type": "module",
+    "scripts": {
+        "dev": "vite",
+        "build": "tsc && vite build",
+        "lint": "eslint . --ext ts,tsx --report-unused-disable-directives --max-warnings 0",
+        "preview": "vite preview",
+        "generateImageObject": "node src/utils/generateImportImages.js"
+    },
+    "dependencies": {
+        "axios": "^1.6.8",
+        "react": "^18.2.0",
+        "react-dom": "^18.2.0",
+        "styled-components": "^6.1.8"
+    },
+    "devDependencies": {
+        "@types/node": "^20.12.2",
+        "@types/react": "^18.2.66",
+        "@types/react-dom": "^18.2.22",
+        "@typescript-eslint/eslint-plugin": "^7.2.0",
+        "@typescript-eslint/parser": "^7.2.0",
+        "@vitejs/plugin-react": "^4.2.1",
+        "eslint": "^8.57.0",
+        "eslint-plugin-react-hooks": "^4.6.0",
+        "eslint-plugin-react-refresh": "^0.4.6",
+        "typescript": "^5.2.2",
+        "vite": "^5.2.0"
+    }
+}

src/problem2/src/App.css

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+#root {
+}
+
+.logo {
+    height: 6em;
+    padding: 1.5em;
+    will-change: filter;
+    transition: filter 300ms;
+}
+.logo:hover {
+    filter: drop-shadow(0 0 2em #646cffaa);
+}
+.logo.react:hover {
+    filter: drop-shadow(0 0 2em #61dafbaa);
+}
+
+@keyframes logo-spin {
+    from {
+        transform: rotate(0deg);
+    }
+    to {
+        transform: rotate(360deg);
+    }
+}
+
+@media (prefers-reduced-motion: no-preference) {
+    a:nth-of-type(2) .logo {
+        animation: logo-spin infinite 20s linear;
+    }
+}
+
+.card {
+    padding: 2em;
+}
+
+.read-the-docs {
+    color: #888;
+}

src/problem2/src/App.tsx

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+import "./App.css";
+import SwapPage from "./pages/SwapPage/SwapPage";
+
+function App() {
+    return <SwapPage />;
+}
+
+export default App;