Problems › JavaScript › events
How many active weekdays in a span
A project runs for a number of calendar days but only counts effort on specified weekdays. Return the number of active days.
- activeDays lists weekday numbers 0 (Monday) through 6 (Sunday).
- Calendar day 0 is the first day; day d falls on weekday d mod 7.
- Count every day in 0 .. days−1 whose weekday appears in activeDays.
- An empty activeDays list means no days count.
activeDayCount(activeDays: list<int>, days: int) → int
Where you start
function activeDayCount(activeDays, days) {
}Worked examples
| Call | Result |
|---|---|
activeDayCount([0], 7) | 1 |
activeDayCount([0,2,4], 7) | 3 |
activeDayCount([0,2,4], 10) | 5 |
activeDayCount([3], 1) | 0 |
Hint
Build a 7-slot lookup array of booleans once, then loop over the days and test each weekday against it.
Reference solution in JavaScript
function activeDayCount(activeDays, days) {
const active = [false, false, false, false, false, false, false];
for (const d of activeDays) active[d] = true;
let count = 0;
for (let i = 0; i < days; i++) if (active[i % 7]) count++;
return count;
}