2637. Promise Time Limit

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2637. Promise Time Limit

題目描述

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

A time limited function is a function that is identical to the original unless it takes longer than t milliseconds to fullfill. In that case, it will reject with "Time Limit Exceeded". Note that it should reject with a string, not an Error.

範例

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:
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

解答

TypeScript

function timeLimit(fn: Fn, t: number): Fn {
  return async function (...args) {
    return new Promise(async (resolve, reject) => {
      const timer = setTimeout(() => {
        reject('Time Limit Exceeded');
      }, t);

      fn(...args)
        .then((res) => {
          clearTimeout(timer);
          resolve(res);
        })
        .catch((err) => {
          clearTimeout(timer);
          reject(err);
        });
    });
  };
}

使用 Promise.race 方法

function timeLimit(fn: Fn, t: number): Fn {
  return async function (...args) {
    const timer = new Promise((_, reject) => setTimeout(() => reject('Time Limit Exceeded'), t));

    return Promise.race([fn(...args), timer]);
  };
}

SheepTues, May 16, 2023

Reference

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