2725. Interval Cancellation

Problem

Given a function fn, an array of arguments args, and an interval time t, return a cancel function cancelFn.

The function fn should be called with args immediately and then called again every t milliseconds until cancelFn is called at cancelT ms.

Example 1:

Input: fn = (x) => x * 2, args = [4], t = 20, cancelT = 110
Output:
[
   {"time": 0, "returned": 8},
   {"time": 20, "returned": 8},
   {"time": 40, "returned": 8},
   {"time": 60, "returned": 8},
   {"time": 80, "returned": 8},
   {"time": 100, "returned": 8}
]
Explanation:
const cancel = cancellable(x => x * 2, [4], 20);
setTimeout(cancel, 110);

Every 20ms, fn(4) is called. Until t=110ms, then it is cancelled.
1st fn call is at 0ms. fn(4) returns 8.
2nd fn call is at 20ms. fn(4) returns 8.
3rd fn call is at 40ms. fn(4) returns 8.
4th fn call is at 60ms. fn(4) returns 8.
5th fn call is at 80ms. fn(4) returns 8.
6th fn call is at 100ms. fn(4) returns 8.
Cancelled at 110ms

Example 2:

Input: fn = (x1, x2) => (x1 * x2), args = [2, 5], t = 25, cancelT = 140
Output:
[
   {"time": 0, "returned": 10},
   {"time": 25, "returned": 10},
   {"time": 50, "returned": 10},
   {"time": 75, "returned": 10},
   {"time": 100, "returned": 10},
   {"time": 125, "returned": 10}
]
Explanation:
const cancel = cancellable((x1, x2) => (x1 * x2), [2, 5], 25);
setTimeout(cancel, 140);

Every 25ms, fn(2, 5) is called. Until t=140ms, then it is cancelled.
1st fn call is at 0ms 
2nd fn call is at 25ms 
3rd fn call is at 50ms 
4th fn call is at 75ms 
5th fn call is at 100ms 
6th fn call is at 125ms
Cancelled at 140ms

Example 3:

Input: fn = (x1, x2, x3) => (x1 + x2 + x3), args = [5, 1, 3], t = 50, cancelT = 180
Output:
[
   {"time": 0, "returned": 9},
   {"time": 50, "returned": 9},
   {"time": 100, "returned": 9},
   {"time": 150, "returned": 9}
]
Explanation:
const cancel = cancellable((x1, x2, x3) => (x1 + x2 + x3), [5, 1, 3], 50);
setTimeout(cancel, 180);

Every 50ms, fn(5, 1, 3) is called. Until t=180ms, then it is cancelled.
1st fn call is at 0ms
2nd fn call is at 50ms
3rd fn call is at 100ms
4th fn call is at 150ms
Cancelled at 180ms

Constraints:

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

Solution (Javascript)

/**
 * @param {Function} fn
 * @param {Array} args
 * @param {number} t
 * @return {Function}
 */
var cancellable = function (fn, args, t) {
  fn(...args);
  let timer = setInterval(() => fn(...args), t);

  let cancelFn = () => clearInterval(timer);
  return cancelFn;
};

/**
 *  const result = []
 *
 *  const fn = (x) => x * 2
 *  const args = [4], t = 20, cancelT = 110
 *
 *  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);
 *
 *  setTimeout(() => {
 *     cancel()
 *  }, cancelT)
 *
 *  setTimeout(() => {
 *    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 + t + 15)
 */

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).