First Day Where You Have Been in All the Rooms
There are n rooms you need to visit, labeled from 0 to n - 1. Each day is labeled, starting from 0. You will go in and visit one room a day.
Initially on day 0, you visit room 0. The order you visit the rooms for the coming days is determined by the following rules and a given 0-indexed array nextVisit of length n:
- Assuming that on a day, you visit room
i: - If you have been in room
ian odd number of times (including the current visit), on the next day you will visit a room with a lower or equal room number specified bynextVisit[i], where0 <= nextVisit[i] <= i. - If you have been in room
ian even number of times (including the current visit), on the next day you will visit room(i + 1) mod n.
Return the label of the first day where you have been in all the rooms. It can be shown that such a day exists. Since the answer may be very large, return it modulo 10^9 + 7.
Example 1
Input
nextVisit = [0,0]Output
2After visiting room 0 on days 0 and 1, day 2 is the first day room 1 is visited, so all rooms have been visited.
Example 2
Input
nextVisit = [0,0,2]Output
6The room visiting order begins
[0, 0, 1, 0, 0, 1, 2, ...], so day 6 is the first day where all rooms have been visited.Constraints
- n == nextVisit.length
- 2 <= n <= 10^5
- 0 <= nextVisit[i] <= i