Is Sleep easy or hard?

Sleep is classified as an Easy problem. The challenge is recognizing the correct async primitive—such as Promise with setTimeout—rather than implementing any complex algorithm or data structure.

Sleep Python/Java solution

In Python, define an async function and call await asyncio.sleep(milliseconds / 1000). In Java, use CompletableFuture with a delayed executor or scheduled task to resolve after the delay. Both rely on non-blocking asynchronous scheduling.

How to solve Sleep in O(1)?

Create a promise that resolves after a timer fires. In JavaScript, call setTimeout inside a Promise and resolve it after the given milliseconds. Since the code only schedules a timer without loops or additional data structures, the complexity stays O(1).

What is the best approach for Sleep?

The standard approach uses a Promise wrapped around setTimeout. The function returns new Promise(resolve => setTimeout(resolve, millis)), which schedules a timer and resolves after the delay. This integrates cleanly with async/await and runs in O(1) time and O(1) space.

Is Sleep asked at Google/Amazon/Meta?

Sleep-style problems appear in JavaScript or async programming interviews, especially for frontend or full-stack roles. Companies like Amazon and Meta often test understanding of promises, event loops, and asynchronous execution patterns.

What data structure is used in Sleep?

No specialized data structure is required. The solution relies on asynchronous runtime primitives such as timers, promises, tasks, or futures that are managed internally by the language runtime or event loop.

What is the time complexity of Sleep?

The algorithmic complexity is O(1) time and O(1) space because the function only schedules a timer. The runtime environment handles the delay through the event loop or scheduler rather than executing additional computation.

2621. Sleep - Practice Online

Given a positive integer millis, write an asynchronous function that sleeps for millis milliseconds. It can resolve any value.

Example 1:

Input: millis = 100
Output: 100
Explanation: It should return a promise that resolves after 100ms.
let t = Date.now();
sleep(100).then(() => {
  console.log(Date.now() - t); // 100
});

Example 2:

Input: millis = 200
Output: 200
Explanation: It should return a promise that resolves after 200ms.

Constraints:

1 <= millis <= 1000