Check if times overlap using moment?

Question

I have an array of [start_time, end_time] time ranges like so:

let timeSegments = [];
timeSegments.push(["02:00", "07:00"])
timeSegments.push(["03:00", "04:00"])

These time segments overlap, since 2AM - 7AM includes 3AM - 4AM

Likewise:

let timeSegments = [];
timeSegments.push(["14:00", "18:00"])
timeSegments.push(["15:00", "19:00"])

2PM to 6PM overlaps with 3PM to 7PM.

I'm using the momentjs library, and would like to know a way to determine if my timeSegments array contains any timeSegments that overlap? The timeSegments array can contain at most 10 [start_time, end_time] pairs. Thanks!

I'd just like to know if any segments overlap (true/false), I don't need to know which of the segments overlap etc.

Answer 1

You can sort timeSegments by start_time (using Array.prototype.sort) and iterate through the sorted list and check if end_time of the current timeSegment is greater than start_time of the next one.

If that happens, there is an overlap.

You can see an example of implementation below:

const checkOverlap = (timeSegments) => {
  if (timeSegments.length === 1) return false;

  timeSegments.sort((timeSegment1, timeSegment2) =>
    timeSegment1[0].localeCompare(timeSegment2[0])
  );

  for (let i = 0; i < timeSegments.length - 1; i++) {
    const currentEndTime = timeSegments[i][1];
    const nextStartTime = timeSegments[i + 1][0];

    if (currentEndTime > nextStartTime) {
      return true;
    }
  }

  return false;
};

const timeSegments1 = [
  ["03:00", "04:00"],
  ["02:00", "07:00"],
  ["12:00", "15:00"]
];

const timeSegments2 = [
  ["05:00", "07:00"],
  ["03:00", "04:00"],
  ["12:00", "15:00"]
];

console.log(checkOverlap(timeSegments1)); // prints true
console.log(checkOverlap(timeSegments2)); // prints false

Note that Array.prototype.sort mutates the array, performing the sort in-place. If you want to preserve the array passed to checkOverlap (which is, in general, a good practice), you can create a copy of timeSegments (using the spread syntax, for example):

const sortedTimeSegments = [...timeSegments].sort(...);