Westgate Resorts wants to determine the minimum number of rooms required to honor a set of reservations without moving guests between rooms. Each reservation has a check-in time and a check-out time. Return the minimum number of rooms needed so that every reservation can be assigned a room.
A room becomes available at the exact check-out time, so a reservation beginning at that time can reuse the room.
Implement min_rooms(reservations), where reservations is a list of two-element lists. Each reservation is represented as [check_in, check_out], with integer time values. Return an integer representing the maximum number of reservations that overlap at any instant.
def min_rooms(reservations):