Seat Reservation Manager

import heapq

class SeatManager:

    def __init__(self, n):
        self.available = [1 + ix for ix in range(n)]
        heapq.heapify(self.available)

    def reserve(self):
        return heapq.heappop(self.available)

    def unreserve(self, seatNumber):
        heapq.heappush(self.available, seatNumber)