LeetCode in Kotlin

2715. Timeout Cancellation

Easy

Given a function fn, an array of arguments args, and a timeout t in milliseconds, return a cancel function cancelFn.

After a delay of t, fn should be called with args passed as parameters unless cancelFn was invoked before the delay of t milliseconds elapses, specifically at cancelT ms. In that case, fn should never be called.

Example 1:

Input: fn = (x) => x * 5, args = [2], t = 20, cancelT = 50

Output: [{“time”: 20, “returned”: 10}]

Explanation:

const cancel = cancellable((x) => x \* 5, [2], 20); // fn(2) called at t=20ms 
setTimeout(cancel, 50); 

The cancellation was scheduled to occur after a delay of cancelT (50ms), which happened after the execution of fn(2) at 20ms.

Example 2:

Input: fn = (x) => x**2, args = [2], t = 100, cancelT = 50

Output: []

Explanation:

const cancel = cancellable((x) => x\*\*2, [2], 100); // fn(2) not called
setTimeout(cancel, 50); 

The cancellation was scheduled to occur after a delay of cancelT (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, cancelT = 100

Output: [{“time”: 30, “returned”: 8}]

Explanation:

const cancel = cancellable((x1, x2) => x1 \* x2, [2,4], 30); // fn(2,4) called at t=30ms 
setTimeout(cancel, 100); 

The cancellation was scheduled to occur after a delay of cancelT (100ms), which happened after the execution of fn(2,4) at 30ms.

Constraints:

• fn is a function
• args is a valid JSON array
• 1 <= args.length <= 10
• 20 <= t <= 1000
• 10 <= cancelT <= 1000

Solution

function cancellable(fn: Function, args: any[], t: number): Function {
    let cancelled: boolean = false
    setTimeout(() => {
        if (!cancelled) {
            fn(...args)
        }
    }, t)
    return () => {
        cancelled = true
    }
}

/*
 *  const result = []
 *
 *  const fn = (x) => x * 5
 *  const args = [2], t = 20, cancelT = 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, cancelT)
 *
 *  setTimeout(() => {
 *     cancel()
 *  }, cancelT)
 *
 *  setTimeout(() => {
 *     console.log(result) // [{"time":20,"returned":10}]
 *  }, maxT + 15)
 */

export { cancellable }

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