LeetCode in Kotlin

2637. Promise Time Limit

Medium

Given an asynchronous function fn and a time t in milliseconds, return a new time limited version of the input function. fn takes arguments provided to the **time limited **function.

The time limited function should follow these rules:

• If the fn completes within the time limit of t milliseconds, the time limited function should resolve with the result.
• If the execution of the fn exceeds the time limit, the time limited function should reject with the string "Time Limit Exceeded".

Example 1:

Input:

fn = async (n) => { 
    await new Promise(res => setTimeout(res, 100)); 
    return n * n; 
} 

inputs = [5]

t = 50

Output: {“rejected”:”Time Limit Exceeded”,”time”:50}

Explanation:

const limited = timeLimit(fn, t) 
const start = performance.now() 
let result; 
try { 
    const res = await limited(...inputs) 
    result = {"resolved": res, "time": Math.floor(performance.now() - start)}; 
} catch (err) { 
    result = {"rejected": err, "time": Math.floor(performance.now() - start)}; 
} 
console.log(result) // Output 

The provided function is set to resolve after 100ms. However, the time limit is set to 50ms. It rejects at t=50ms because the time limit was reached.

Example 2:

Input:

fn = async (n) => { 
    await new Promise(res => setTimeout(res, 100)); 
    return n * n; 
} 

inputs = [5]

t = 150

Output: {“resolved”:25,”time”:100}

Explanation: The function resolved 5 * 5 = 25 at t=100ms. The time limit is never reached.

Example 3:

Input:

fn = async (a, b) => { 
    await new Promise(res => setTimeout(res, 120)); 
    return a + b; 
} 

inputs = [5,10]

t = 150

Output: {“resolved”:15,”time”:120}

Explanation: The function resolved 5 + 10 = 15 at t=120ms. The time limit is never reached.

Example 4:

Input:

fn = async () => { 
    throw "Error"; 
} 

inputs = []

t = 1000

Output: {“rejected”:”Error”,”time”:0}

Explanation: The function immediately throws an error.

Constraints:

• 0 <= inputs.length <= 10
• 0 <= t <= 1000
• fn returns a promise

Solution

type Fn = (...params: any[]) => Promise<any>

function timeLimit(fn: Fn, t: number): Fn {
    return async function (...args) {
        const timeout = new Promise<any>((_, reject) => {
            setTimeout(() => {
                reject('Time Limit Exceeded') //NOSONAR
            }, t)
        })
        return Promise.race([fn(...args), timeout])
    }
}

/*
 * const limited = timeLimit((t) => new Promise(res => setTimeout(res, t)), 100);
 * limited(150).catch(console.log) // "Time Limit Exceeded" at t=100ms
 */

export { timeLimit }

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