{leetcode}/problems/first-day-where-you-have-been-in-all-the-rooms/[LeetCode - 1997. 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 109 + 7.
Example 1:
Input: nextVisit = [0,0] Output: 2 Explanation: - On day 0, you visit room 0. The total times you have been in room 0 is 1, which is odd. On the next day you will visit room nextVisit[0] = 0 - On day 1, you visit room 0, The total times you have been in room 0 is 2, which is even. On the next day you will visit room (0 + 1) mod 2 = 1 - On day 2, you visit room 1. This is the first day where you have been in all the rooms.
Example 2:
Input: nextVisit = [0,0,2] Output: 6 Explanation: Your room visiting order for each day is: [0,0,1,0,0,1,2,...]. Day 6 is the first day where you have been in all the rooms.
Example 3:
Input: nextVisit = [0,1,2,0] Output: 6 Explanation: Your room visiting order for each day is: [0,0,1,1,2,2,3,...]. Day 6 is the first day where you have been in all the rooms.
Constraints:
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n == nextVisit.length -
2 ⇐ n ⇐ 105 -
0 ⇐ nextVisit[i] ⇐ i