Package g1901_2000.s1997_first_day_where_you_have_been_in_all_the_rooms

Class Solution

  • public class Solution
extends Object
    1997 - First Day Where You Have Been in All the Rooms.

    Medium

    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 i an 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 by nextVisit[i] where 0 <= nextVisit[i] <= i;
    • if you have been in room i an 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:

    • n == nextVisit.length
    • 2 <= n <= 105
    • 0 <= nextVisit[i] <= i

    • Constructor Detail

      • Solution

        public Solution()

    • Method Detail

      • firstDayBeenInAllRooms

        public int firstDayBeenInAllRooms​(int[] nextVisit)