Is Add Two Promises easy or hard?

Add Two Promises is considered an easy problem. It mainly tests basic knowledge of JavaScript promises and asynchronous handling rather than complex algorithms or data structures.

Add Two Promises Python/Java solution

The original problem targets JavaScript because it relies on Promise behavior. In Python, a similar pattern would use asyncio.gather with coroutines, while Java would use CompletableFuture.allOf to combine asynchronous computations.

How to solve Add Two Promises in O(1)?

Use Promise.all to resolve both promises simultaneously. Once both values are returned, add them and return the result. The operation performs a constant number of asynchronous resolutions and arithmetic operations, giving O(1) time and space complexity.

What is the best approach for Add Two Promises?

Using Promise.all is the best approach. It resolves both promises concurrently and returns their results in an array, allowing you to compute the sum immediately. This keeps the implementation concise and avoids unnecessary sequential waiting.

Is Add Two Promises asked at Google/Amazon/Meta?

Problems involving promises and async control flow frequently appear in JavaScript interviews at companies like Google, Amazon, and Meta. While this exact problem may vary, understanding Promise.all and async/await is commonly tested.

What data structure is used in Add Two Promises?

No specialized data structure is required. The problem focuses on JavaScript asynchronous primitives such as Promise objects and utilities like Promise.all that coordinate multiple promise resolutions.

What is the time complexity of Add Two Promises?

The computational complexity is O(1) time and O(1) space because only two values are processed. In terms of asynchronous execution, the total wait time equals the slower of the two promises since they can resolve in parallel.

Description Solution Video 18:13

2723. Add Two Promises

Easy91.5% acceptance5 companies

Given two promises promise1 and promise2, return a new promise. promise1 and promise2 will both resolve with a number. The returned promise should resolve with the sum of the two numbers.

Example 1:

Input: 
promise1 = new Promise(resolve => setTimeout(() => resolve(2), 20)), 
promise2 = new Promise(resolve => setTimeout(() => resolve(5), 60))
Output: 7
Explanation: The two input promises resolve with the values of 2 and 5 respectively. The returned promise should resolve with a value of 2 + 5 = 7. The time the returned promise resolves is not judged for this problem.

Example 2:

Input: 
promise1 = new Promise(resolve => setTimeout(() => resolve(10), 50)), 
promise2 = new Promise(resolve => setTimeout(() => resolve(-12), 30))
Output: -2
Explanation: The two input promises resolve with the values of 10 and -12 respectively. The returned promise should resolve with a value of 10 + -12 = -2.

Constraints:

promise1 and promise2 are promises that resolve with a number

Asked at 5 companies

Google Amazon Microsoft Meta Bloomberg

18:13

Still stuck?Read 5 approaches, or watch a walkthrough.

Open solution

LanguageLoading editor…

1/**
2 * @param {Promise} promise1
3 * @param {Promise} promise2
4 * @return {Promise}
5 */
6var addTwoPromises = async function(promise1, promise2) {
7    
8};
9 
10/**
11 * addTwoPromises(Promise.resolve(2), Promise.resolve(2))
12 *   .then(console.log); // 4
13 */

Starter codeJavaScriptSpaces: 4

Examples

Case 1Case 2

Input

new Promise(resolve => setTimeout(() => resolve(2), 20))
new Promise(resolve => setTimeout(() => resolve(5), 60))

Input

new Promise(resolve => setTimeout(() => resolve(10), 50))
new Promise(resolve => setTimeout(() => resolve(-12), 30))

Your code is saved on this device.Solution