+ );
+}
diff --git a/src/problem2/src/main.jsx b/src/problem2/src/main.jsx
new file mode 100644
index 0000000000..4ecd9cfb14
--- /dev/null
+++ b/src/problem2/src/main.jsx
@@ -0,0 +1,10 @@
+import React from "react";
+import { createRoot } from "react-dom/client";
+import App from "./App.jsx";
+import "./styles.css";
+
+createRoot(document.getElementById("root")).render(
+
+
+
+);
diff --git a/src/problem2/src/styles.css b/src/problem2/src/styles.css
new file mode 100644
index 0000000000..9c644a3675
--- /dev/null
+++ b/src/problem2/src/styles.css
@@ -0,0 +1,48 @@
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+@layer base {
+ :root {
+ color-scheme: light;
+ }
+
+ * {
+ box-sizing: border-box;
+ }
+
+ body {
+ @apply m-0 min-h-screen min-w-[360px] bg-slate-100 font-sans text-slate-950 antialiased;
+ background-image:
+ radial-gradient(620px 320px at 50% 0%, rgba(37, 99, 235, 0.12), transparent 60%),
+ linear-gradient(180deg, rgba(255, 255, 255, 0.72), rgba(255, 255, 255, 0));
+ }
+
+ button,
+ input,
+ select {
+ font: inherit;
+ }
+
+ ::selection {
+ background: rgba(37, 99, 235, 0.22);
+ }
+}
+
+@layer components {
+ .surface {
+ @apply rounded-2xl border border-slate-200/80 bg-white shadow-swap;
+ }
+
+ .surface-outline {
+ @apply ring-1 ring-slate-900/5;
+ }
+
+ .focus-ring {
+ @apply focus:outline-none focus-visible:ring-4 focus-visible:ring-accent/20;
+ }
+
+ .subtle-divider {
+ @apply h-px w-full bg-gradient-to-r from-transparent via-ink/10 to-transparent;
+ }
+}
diff --git a/src/problem2/src/utils/format.js b/src/problem2/src/utils/format.js
new file mode 100644
index 0000000000..0aa49d4ae1
--- /dev/null
+++ b/src/problem2/src/utils/format.js
@@ -0,0 +1,18 @@
+export function formatNumber(value, maximumDigits = 6) {
+ return new Intl.NumberFormat("en-US", {
+ maximumFractionDigits: maximumDigits,
+ minimumFractionDigits: 0
+ }).format(value);
+}
+
+export function formatCurrency(value) {
+ return new Intl.NumberFormat("en-US", {
+ style: "currency",
+ currency: "USD",
+ maximumFractionDigits: value >= 1 ? 2 : 6
+ }).format(value);
+}
+
+export function parseFormattedNumber(value) {
+ return Number(String(value).replace(/,/g, ""));
+}
diff --git a/src/problem2/src/utils/swap.js b/src/problem2/src/utils/swap.js
new file mode 100644
index 0000000000..1e558ced53
--- /dev/null
+++ b/src/problem2/src/utils/swap.js
@@ -0,0 +1,50 @@
+const MOCK_BALANCES = [2.8, 1200, 460, 88, 15400, 940, 38, 720];
+
+export function createBalances(tokens) {
+ // Mock wallet balances for this frontend-only challenge.
+ return tokens.reduce((result, token, index) => {
+ result[token.symbol] = MOCK_BALANCES[index % MOCK_BALANCES.length];
+ return result;
+ }, {});
+}
+
+export function calculateOutput(amount, fromToken, toToken) {
+ if (!amount || !fromToken || !toToken) {
+ return 0;
+ }
+
+ return (amount * fromToken.price) / toToken.price;
+}
+
+export function validateSwap({ amountText, amount, balance, fromSymbol, toSymbol }) {
+ if (!fromSymbol || !toSymbol) {
+ return "";
+ }
+
+ if (fromSymbol === toSymbol) {
+ return "Choose two different currencies.";
+ }
+
+ if (amountText !== "") {
+ const trimmed = String(amountText).trim();
+
+ // Allow partial inputs like "." while the user is typing.
+ if (trimmed === ".") {
+ return "";
+ }
+
+ if (!Number.isFinite(amount)) {
+ return "Enter a valid number.";
+ }
+
+ if (amount <= 0) {
+ return "Enter an amount greater than zero.";
+ }
+ }
+
+ if (amount > balance) {
+ return `Insufficient ${fromSymbol} balance.`;
+ }
+
+ return "";
+}
diff --git a/src/problem2/style.css b/src/problem2/style.css
deleted file mode 100644
index 915af91c72..0000000000
--- a/src/problem2/style.css
+++ /dev/null
@@ -1,8 +0,0 @@
-body {
- display: flex;
- flex-direction: row;
- align-items: center;
- justify-content: center;
- min-width: 360px;
- font-family: Arial, Helvetica, sans-serif;
-}
diff --git a/src/problem2/tailwind.config.js b/src/problem2/tailwind.config.js
new file mode 100644
index 0000000000..6b9535c94f
--- /dev/null
+++ b/src/problem2/tailwind.config.js
@@ -0,0 +1,27 @@
+/** @type {import('tailwindcss').Config} */
+export default {
+ content: [
+ "./index.html",
+ "./src/**/*.{js,jsx}"
+ ],
+ theme: {
+ extend: {
+ colors: {
+ ink: "#142019",
+ muted: "#66736b",
+ line: "#dce5dd",
+ soft: "#f4f8f5",
+ accent: {
+ DEFAULT: "#2563eb",
+ dark: "#1d4ed8",
+ soft: "#dbeafe"
+ }
+ },
+ boxShadow: {
+ swap: "0 18px 48px rgba(20, 32, 25, 0.12)",
+ route: "0 18px 40px rgba(20, 32, 25, 0.08)"
+ }
+ }
+ },
+ plugins: []
+};
diff --git a/src/problem2/vite.config.js b/src/problem2/vite.config.js
new file mode 100644
index 0000000000..db1b19eebb
--- /dev/null
+++ b/src/problem2/vite.config.js
@@ -0,0 +1,6 @@
+import { defineConfig } from "vite";
+import react from "@vitejs/plugin-react";
+
+export default defineConfig({
+ plugins: [react()]
+});
diff --git a/src/problem3/README.md b/src/problem3/README.md
new file mode 100644
index 0000000000..245ba6d23c
--- /dev/null
+++ b/src/problem3/README.md
@@ -0,0 +1,163 @@
+# Problem 3: Messy React
+
+## Issues found
+
+1. `WalletBalance` is missing the `blockchain` field.
+
+ The code calls `balance.blockchain`, but the interface only defines `currency` and `amount`. This breaks TypeScript correctness and hides a real data-shape problem.
+
+2. `getPriority` uses `any`.
+
+ `blockchain: any` removes type safety. It should be typed as a known blockchain string union or at least `string`.
+
+3. `getPriority` is recreated on every render.
+
+ The function is declared inside the component. This is not a major issue by itself, but it is unnecessary because the priority mapping is static. Moving it outside the component is cleaner and avoids repeated allocation.
+
+4. The filter logic references an undefined variable.
+
+ `lhsPriority` does not exist inside the filter callback. The intended variable is probably `balancePriority`.
+
+5. The filter condition is logically wrong.
+
+ The current code returns `true` when `balance.amount <= 0`, meaning it keeps zero or negative balances and removes positive balances. For a wallet list, the expected behavior is usually to keep balances with `amount > 0`.
+
+6. The filter is harder to read than necessary.
+
+ Nested `if` statements can be replaced with a direct boolean expression:
+
+ ```ts
+ getPriority(balance.blockchain) > -99 && balance.amount > 0
+ ```
+
+7. `sort` comparator can return `undefined`.
+
+ If two priorities are equal, the comparator returns nothing. A comparator should always return a number. This can lead to unstable or inconsistent sorting behavior.
+
+8. `prices` is included in the `useMemo` dependency array unnecessarily.
+
+ `sortedBalances` does not use `prices`, so adding `prices` causes the filtering and sorting work to rerun whenever prices change.
+
+9. `formattedBalances` is calculated but not used.
+
+ The code creates `formattedBalances`, but then maps over `sortedBalances` when rendering rows. Because of this, `balance.formatted` is unavailable in `rows`.
+
+10. The `rows` map uses the wrong type.
+
+ `sortedBalances` contains `WalletBalance`, but the callback types `balance` as `FormattedWalletBalance`. That is incorrect unless the formatted data is actually used.
+
+11. Using array index as React key is an anti-pattern.
+
+ `key={index}` can cause incorrect row reuse when the list order changes. A stable key such as `currency` or `blockchain-currency` should be used.
+
+12. `children` is destructured but never rendered.
+
+ The component removes `children` from `props`, but does not render it. This can surprise callers and makes `Props extends BoxProps` less useful.
+
+13. `Props` is empty.
+
+ `interface Props extends BoxProps {}` adds no new information. A type alias would be simpler unless extra props are expected later.
+
+14. Formatting work is not memoized.
+
+ Formatting balances and building rows happen on every render. For small lists this is fine, but since the task asks about computational inefficiencies, the derived wallet row data should be memoized.
+
+15. The formatted amount uses default `toFixed()`.
+
+ `toFixed()` defaults to zero decimal places. That may be fine for whole-number tokens, but most token balances need a defined precision such as `toFixed(2)` or a formatter.
+
+16. There is no fallback for missing prices.
+
+ `prices[balance.currency] * balance.amount` becomes `NaN` if a token price is missing. It should default to `0` or handle unavailable prices explicitly.
+
+17. `classes.row` is used but not defined in the snippet.
+
+ This may be defined outside the snippet, but as shown, it is an undeclared dependency.
+
+18. The indentation and formatting are inconsistent.
+
+ Mixed tabs/spaces and missing semicolons make the code harder to review and maintain.
+
+## Refactored version
+
+```tsx
+interface WalletBalance {
+ currency: string;
+ amount: number;
+ blockchain: string;
+}
+
+interface FormattedWalletBalance extends WalletBalance {
+ formatted: string;
+ usdValue: number;
+}
+
+type Prices = Record;
+type Props = BoxProps;
+
+// Assumes BoxProps, WalletRow, useWalletBalances, usePrices, and classes are provided by the app.
+const BLOCKCHAIN_PRIORITIES: Record = {
+ Osmosis: 100,
+ Ethereum: 50,
+ Arbitrum: 30,
+ Zilliqa: 20,
+ Neo: 20
+};
+
+const getPriority = (blockchain: string): number => {
+ return BLOCKCHAIN_PRIORITIES[blockchain] ?? -99;
+};
+
+const WalletPage: React.FC = ({ children, ...rest }) => {
+ const balances = useWalletBalances();
+ const prices: Prices = usePrices();
+
+ const sortedBalances = useMemo(() => {
+ return balances
+ .filter((balance: WalletBalance) => {
+ return getPriority(balance.blockchain) > -99 && balance.amount > 0;
+ })
+ .sort((lhs: WalletBalance, rhs: WalletBalance) => {
+ return getPriority(rhs.blockchain) - getPriority(lhs.blockchain);
+ });
+ }, [balances]);
+
+ const formattedBalances = useMemo(() => {
+ return sortedBalances.map((balance: WalletBalance) => {
+ const price = prices[balance.currency] ?? 0;
+
+ return {
+ ...balance,
+ formatted: balance.amount.toFixed(2),
+ usdValue: price * balance.amount
+ };
+ });
+ }, [sortedBalances, prices]);
+
+ return (
+