feat: 2621 problem

Author: shahadathhs

README.md

@@ -36,18 +36,6 @@ pnpm test
 pnpm test:problem 2618
 ```
 
-### 4. Development CLI
-
-```bash
-pnpm dev
-```
-
-This starts `src/main.ts`, which accepts a problem number:
-
-```bash
-pnpm dev 2618
-```
-
 ---
 
 ## 🤝 Contributing

src/app/2621-sleep.ts

@@ -0,0 +1,35 @@
+// * Title
+// 2621. Sleep
+
+// * Concepts Asynchronous Programming, Promises, setTimeout
+
+// * Description
+/**
+ * Given a positive integer millis, write an asynchronous function that sleeps
+   for millis milliseconds. It can resolve any value.
+
+Note that minor deviation from millis in the actual sleep duration is
+acceptable.
+*/
+
+// * Hints
+/**
+ * 1. In Javascript, you can execute code after some delay with the
+ *    setTimeout(fn, sleepTime) function.
+ * 2. An async function is defined as function which returns a Promise.
+ * 3. To create a Promise, you can code new Promise((resolve, reject) => {}).
+ *    When you want the function to return a value, code resolve(value) inside
+ *    the callback.
+ */
+
+// * Link to the problem: https://leetcode.com/problems/sleep/description
+
+// * Solution
+export type SleepFunction = (millis: number) => Promise<void>;
+
+async function sleep(millis: number): Promise<void> {
+  return new Promise(resolve => setTimeout(resolve, millis));
+}
+
+// * Export the function
+export { sleep };