2715. 执行可取消的延迟函数
2715. 执行可取消的延迟函数
题目
Given a function fn
, an array of arguments args
, and a timeout t
in milliseconds, return a cancel function cancelFn
.
After a delay of cancelTimeMs
, the returned cancel function cancelFn
will be invoked.
setTimeout(cancelFn, cancelTimeMs)
Initially, the execution of the function fn
should be delayed by t
milliseconds.
If, before the delay of t
milliseconds, the function cancelFn
is invoked, it should cancel the delayed execution of fn
. Otherwise, if cancelFn
is not invoked within the specified delay t
, fn
should be executed with the provided args
as arguments.
Example 1:
Input: fn = (x) => x * 5, args = [2], t = 20
Output: [{"time": 20, "returned": 10}]
Explanation:
const cancelTimeMs = 50;
const cancelFn = cancellable((x) => x * 5, [2], 20);
setTimeout(cancelFn, cancelTimeMs);
The cancellation was scheduled to occur after a delay of cancelTimeMs (50ms), which happened after the execution of fn(2) at 20ms.
Example 2:
Input: fn = (x) => x**2, args = [2], t = 100
Output: []
Explanation:
const cancelTimeMs = 50;
const cancelFn = cancellable((x) => x**2, [2], 100);
setTimeout(cancelFn, cancelTimeMs);
The cancellation was scheduled to occur after a delay of cancelTimeMs (50ms), which happened before the execution of fn(2) at 100ms, resulting in fn(2) never being called.
Example 3:
Input: fn = (x1, x2) => x1 * x2, args = [2,4], t = 30
Output: [{"time": 30, "returned": 8}]
Explanation: const cancelTimeMs = 100;
const cancelFn = cancellable((x1, x2) => x1 * x2, [2,4], 30);
setTimeout(cancelFn, cancelTimeMs);
The cancellation was scheduled to occur after a delay of cancelTimeMs (100ms), which happened after the execution of fn(2,4) at 30ms.
Constraints:
fn
is a functionargs
is a valid JSON array1 <= args.length <= 10
20 <= t <= 1000
10 <= cancelTimeMs <= 1000
题目大意
给定一个函数 fn
,一个参数数组 args
和一个以毫秒为单位的超时时间 t
,返回一个取消函数 cancelFn
。
在 cancelTimeMs
的延迟后,返回的取消函数 cancelFn
将被调用。
setTimeout(cancelFn, cancelTimeMs)
最初,函数 fn
的执行应该延迟 t
毫秒。
如果在 t
毫秒的延迟之前调用了函数 cancelFn
,它应该取消 fn
的延迟执行。否则,如果在指定的延迟 t
内没有调用 cancelFn
,则应执行 fn
,并使用提供的 args
作为参数。
提示:
fn
是一个函数args
是一个有效的 JSON 数组1 <= args.length <= 10
20 <= t <= 1000
10 <= cancelTimeMs <= 1000
解题思路
创建定时器:使用
setTimeout
来执行fn
,并设置延迟t
毫秒后执行。实现取消功能:
setTimeout
会返回一个timer
句柄,可以通过clearTimeout(timer)
来取消该定时器。返回一个取消函数cancelFn
,该函数被调用时会清除定时器,阻止fn
的执行。
复杂度分析
- 时间复杂度:
O(1)
,setTimeout
和clearTimeout
的调用都是常数时间操作。 - 空间复杂度:
O(1)
,存储一个定时器句柄timer
以及取消函数占用常数空间。
代码
/**
* @param {Function} fn
* @param {Array} args
* @param {number} t
* @return {Function}
*/
var cancellable = function (fn, args, t) {
const timer = setTimeout(() => fn(...args), t); // 延迟 t 毫秒后执行 fn
const cancelFn = () => clearTimeout(timer); // 返回取消函数
return cancelFn;
};
/**
* const result = [];
*
* const fn = (x) => x * 5;
* const args = [2], t = 20, cancelTimeMs = 50;
*
* const start = performance.now();
*
* const log = (...argsArr) => {
* const diff = Math.floor(performance.now() - start);
* result.push({"time": diff, "returned": fn(...argsArr)});
* }
*
* const cancel = cancellable(log, args, t);
*
* const maxT = Math.max(t, cancelTimeMs);
*
* setTimeout(cancel, cancelTimeMs);
*
* setTimeout(() => {
* console.log(result); // [{"time":20,"returned":10}]
* }, maxT + 15)
*/