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间隔取消
现给定一个函数 fn ，一个参数数组 args 和一个时间间隔 t ，返回一个取消函数 cancelFn 。 在经过 cancelTimeMs 毫秒的延迟后，将调用返回的取消函数 cancelFn 。 setTimeout(cancelFn, cancelTimeMs) 函数 fn 应立即使用参数 …
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简单 · 区间·cancellation·core·interview·pattern
答案摘要
function cancellable(fn: Function, args: any[], t: number): Function { fn(...args);
Interview AiBoxInterview AiBox 实时 AI 助手，陪你讲清 区间·cancellation·core·interview·pattern 题型思路
题目描述
现给定一个函数 fn，一个参数数组 args 和一个时间间隔 t，返回一个取消函数 cancelFn。
在经过 cancelTimeMs 毫秒的延迟后，将调用返回的取消函数 cancelFn。
setTimeout(cancelFn, cancelTimeMs)
函数 fn 应立即使用参数 args 调用，然后每隔 t 毫秒调用一次，直到在 cancelTimeMs 毫秒时调用 cancelFn。
示例 1：
输入：fn = (x) => x * 2, args = [4], t = 35, cancelT = 190
输出：
[
{"time": 0, "returned": 8},
{"time": 35, "returned": 8},
{"time": 70, "returned": 8},
{"time": 105, "returned": 8},
{"time": 140, "returned": 8},
{"time": 175, "returned": 8}
]
解释：
const cancelTimeMs = 190;
const cancelFn = cancellable((x) => x * 2, [4], 35);
setTimeout(cancelFn, cancelTimeMs);
每隔 35ms，调用 fn(4)。直到 t=190ms，然后取消。
第一次调用 fn 是在 0ms。fn(4) 返回 8。
第二次调用 fn 是在 35ms。fn(4) 返回 8。
第三次调用 fn 是在 70ms。fn(4) 返回 8。
第四次调用 fn 是在 105ms。fn(4) 返回 8。
第五次调用 fn 是在 140ms。fn(4) 返回 8。
第六次调用 fn 是在 175ms。fn(4) 返回 8。
在 t=190ms 时取消
示例 2：
输入：fn = (x1, x2) => (x1 * x2), args = [2, 5], t = 30, cancelT = 165
输出：
[
{"time": 0, "returned": 10},
{"time": 30, "returned": 10},
{"time": 60, "returned": 10},
{"time": 90, "returned": 10},
{"time": 120, "returned": 10},
{"time": 150, "returned": 10}
]
解释：
const cancelTimeMs = 165;
const cancelFn = cancellable((x1, x2) => (x1 * x2), [2, 5], 30)
setTimeout(cancelFn, cancelTimeMs)
每隔 30ms，调用 fn(2, 5)。直到 t=165ms，然后取消。
第一次调用 fn 是在 0ms
第二次调用 fn 是在 30ms
第三次调用 fn 是在 60ms
第四次调用 fn 是在 90ms
第五次调用 fn 是在 120ms
第六次调用 fn 是在 150ms
在 165ms 取消
示例 3：
输入：fn = (x1, x2, x3) => (x1 + x2 + x3), args = [5, 1, 3], t = 50, cancelT = 180
输出：
[
{"time": 0, "returned": 9},
{"time": 50, "returned": 9},
{"time": 100, "returned": 9},
{"time": 150, "returned": 9}
]
解释：
const cancelTimeMs = 180;
const cancelFn = cancellable((x1, x2, x3) => (x1 + x2 + x3), [5, 1, 3], 50)
setTimeout(cancelFn, cancelTimeMs)
每隔 50ms，调用 fn(5, 1, 3)。直到 t=180ms，然后取消。
第一次调用 fn 是在 0ms
第二次调用 fn 是在 50ms
第三次调用 fn 是在 100ms
第四次调用 fn 是在 150ms
在 180ms 取消
提示：
fn是一个函数args是一个有效的 JSON 数组1 <= args.length <= 1030 <= t <= 10010 <= cancelT <= 500
解题思路
方法一
function cancellable(fn: Function, args: any[], t: number): Function {
fn(...args);
const time = setInterval(() => fn(...args), t);
return () => clearInterval(time);
}
/**
* const result = []
*
* const fn = (x) => x * 2
* const args = [4], t = 20, cancelT = 110
*
* const log = (...argsArr) => {
* result.push(fn(...argsArr))
* }
*
* const cancel = cancellable(fn, args, t);
*
* setTimeout(() => {
* cancel()
* console.log(result) // [
* // {"time":0,"returned":8},
* // {"time":20,"returned":8},
* // {"time":40,"returned":8},
* // {"time":60,"returned":8},
* // {"time":80,"returned":8},
* // {"time":100,"returned":8}
* // ]
* }, cancelT)
*/
复杂度分析
| 指标 | 值 |
|---|---|
| 时间 | complexity is dominated by the interval calls, where each interval is triggered once every `t` milliseconds until cancellation. Space complexity is constant, as we're only maintaining a reference to the set interval and the cancel function. |
| 空间 | ** |
面试官常问的追问
外企场景- question_mark
Look for correct handling of repeated execution and cancellation at the right moment.
- question_mark
Watch for the proper use of `setInterval` for periodic execution and `setTimeout` for cancellation.
- question_mark
Ensure that the solution works even for the edge cases involving small or large values for `t` and `cancelTimeMs`.
常见陷阱
外企场景- error
Failing to clear the interval properly can cause the function to continue executing beyond the cancellation time.
- error
Not accounting for edge cases where the cancellation time is too short for multiple executions.
- error
Incorrect handling of the cancel function could lead to premature or delayed cancellation of the repeated function calls.
进阶变体
外企场景- arrow_right_alt
Modify the function to allow multiple functions to be cancelled in sequence.
- arrow_right_alt
Introduce a delay before starting the repeated function calls, not just an immediate execution.
- arrow_right_alt
Add support for dynamic changes to the interval time during execution.