You are given an integer n denoting the number of floors in a building, where the floors are numbered from 0 to n - 1.
You are also given an integer start and a 2D integer array requests, where requests[i] = [arrivali, floori] indicates that a request for floori is made at time arrivali.
At time 0, the elevator is at floor start.
At each second, the elevator may move up by 1 floor, move down by 1 floor, or remain on its current floor.
A request can be fulfilled only at or after its arrival time; it is fulfilled instantly when the elevator is on its requested floor at any time from its arrival time onward.
Return the minimum time needed to fulfill all requests.
Example 1:
Input: n = 9, start = 0, requests = [[0,8],[6,5]]
Output: 9
Explanation:
start) to floor 5 (requests[1][1]) in 5 seconds, reaching at time 5. Since requests[1][0] = 6, wait until time 6 to fulfill it.requests[0][1]) in 3 seconds, fulfilling it at time 9.Thus, all requests are fulfilled by time 9.
Example 2:
Input: n = 8, start = 5, requests = [[1,7],[7,3]]
Output: 7
Explanation:
start) to floor 7 (requests[0][1]) in 2 seconds, reaching at time 2. Since requests[0][0] = 1 has already passed, floor 7 is fulfilled at time 2.requests[1][1]) in 4 seconds, reaching at time 6. Since requests[1][0] = 7, wait until time 7.Thus, all requests are fulfilled by time 7.
Example 3:
Input: n = 7, start = 3, requests = [[0,5],[0,1],[6,3]]
Output: 8
Explanation:
start) to floor 5 (requests[0][1]) in 2 seconds, fulfilling it at time 2.requests[1][1]) in 4 seconds, fulfilling it at time 6.requests[2][1]) in 2 seconds, reaching at time 8. Its request arrived at requests[2][0] = 6, so floor 3 is fulfilled at time 8.Thus, all requests are fulfilled by time 8.
Constraints:
1 <= n <= 1091 <= requests.length <= 16requests[i] == [arrivali, floori]0 <= arrivali <= 1090 <= start, floori <= n - 1