Sleep

Sleep - Problem

JavaScript Easy

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

Note: Minor deviation from millis in the actual sleep duration is acceptable.

Input & Output

Example 1 — Basic Sleep

$ Input: millis = 1000

› Output: "Sleep completed"

💡 Note: Function sleeps for 1000 milliseconds (1 second) and then resolves with a value

Example 2 — Short Sleep

$ Input: millis = 100

› Output: "Sleep completed"

💡 Note: Function sleeps for 100 milliseconds and resolves quickly

Example 3 — Minimal Sleep

$ Input: millis = 1

› Output: "Sleep completed"

💡 Note: Function sleeps for just 1 millisecond, the minimum valid input

Constraints

1 ≤ millis ≤ 1000

Visualization

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Asked in

G Google 25 M Microsoft 20 f Facebook 15 a Amazon 18

The key insight is wrapping setTimeout in a Promise to make it compatible with async/await. Best approach is Promise-based setTimeout for clean asynchronous code. Time: O(1), Space: O(1)

Common Approaches

✓ Callback-based setTimeout

⏱️ Time: O(1) Space: O(1)

The simplest approach using traditional callback-style setTimeout. However, this doesn't integrate well with modern async/await patterns and requires nested callback handling.

Promise-based setTimeout

⏱️ Time: O(1) Space: O(1)

This approach wraps setTimeout in a Promise, making it compatible with modern async/await patterns. The Promise resolves after the specified delay, allowing for clean asynchronous code flow.

Callback-based setTimeout — Algorithm Steps

Use setTimeout with a callback function
Wait for the specified milliseconds
Execute callback when timer expires

Visualization

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Step-by-Step Walkthrough

Setup Timer

setTimeout registers callback for future execution

Wait Period

Timer counts down the specified milliseconds

Execute Callback

Callback function runs when timer expires

Code -

solution.c — C

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>

typedef void (*Callback)(void);

void sleepMillis(int millis, Callback callback) {
    struct timespec req;
    req.tv_sec = millis / 1000;
    req.tv_nsec = (millis % 1000) * 1000000;
    
    nanosleep(&req, NULL);
    
    if (callback != NULL) {
        callback();
    }
}

void onSleepComplete() {
    printf("\"Sleep completed\"\n");
}

int main() {
    char line[100];
    
    if (fgets(line, sizeof(line), stdin) == NULL) return 1;
    
    int millis = atoi(line);
    
    sleepMillis(millis, onSleepComplete);
    
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(1)

Single setTimeout call with constant operations

✓ Linear Growth

Space Complexity

O(1)

Only stores timer reference, no additional data structures

✓ Linear Space

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Input & Output

Constraints

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Related Problems

Common Approaches

Callback-based setTimeout — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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