Problems › JavaScript › dates
Find the first free slot in a day
A scheduling assistant looks at a day of bookings and offers the earliest time a meeting of a given length would fit.
- All times are minutes since midnight. Bookings arrive sorted and do not overlap each other.
- The meeting must fit entirely between the start and end of the working day.
- A meeting may begin the moment a booking ends.
- A length of zero or less, or a day with no room, gives null.
nextFreeSlot(busy: list<Slot>, dayStart: int, dayEnd: int, minutes: int) → int?
Where you start
function nextFreeSlot(busy, dayStart, dayEnd, minutes) {
}Worked examples
| Call | Result |
|---|---|
nextFreeSlot([{"start":540,"end":600}], 480, 1020, 30) | 480 |
nextFreeSlot([{"start":480,"end":540}], 480, 1020, 30) | 540 |
nextFreeSlot([{"start":480,"end":1020}], 480, 1020, 30) | null |
nextFreeSlot([{"start":540,"end":600},{"start":610,"end":700}], 480, 1020, 90) | 700 |
Hint
Sweep a cursor from the start of the day: before each booking, check whether the gap is wide enough, then jump the cursor past it.
Reference solution in JavaScript
function nextFreeSlot(busy, dayStart, dayEnd, minutes) {
if (minutes <= 0) return null;
let cursor = dayStart;
for (const s of busy) {
if (s.start - cursor >= minutes) return cursor;
if (s.end > cursor) cursor = s.end;
}
return dayEnd - cursor >= minutes ? cursor : null;
}