Movie Ticket Booking (BookMyShow)

medium · booking, atomicity, seat map

Brief-reported interview attribution (unverified): Flipkart, Amazon, MakeMyTrip

Design a movie ticket booking system. A show has numbered seats 1..total_seats. Booking a set of seats succeeds only if all of them are free (all-or-nothing); if any seat is taken or invalid, nothing is booked. Cancelling frees the seats. (Payment is out of scope for this problem; booking confirms immediately. In production the check-and-book must be atomic so two users cannot take the same seat — in this single-threaded simulation the method itself is the atomic unit.)

class BookMyShow:
    def __init__(self):
    def add_show(self, show_id, movie, screen, total_seats):
    def available_seats(self, show_id):
        # -> sorted list of free seat numbers ([] for an unknown show)
    def book(self, show_id, user_id, seat_numbers):
        # -> booking id (int, starting at 1), or None if any seat is taken/invalid
        #    or the show is unknown or the seat list is empty
    def cancel(self, booking_id):
        # -> True if the booking was active and is now cancelled, False otherwise
    def booking_details(self, booking_id):
        # -> {"show":, "user":, "seats": [...], "active": bool}, or None

Rules. Seat numbers start at 1. Booking ids start at 1 and increase. A cancelled booking's seats become free again; cancelling twice returns False. booking_details returns the seats in the order they were booked.

Tests use explicit inputs and injected clocks/callbacks. No network, real threads or application-server execution is involved.

Public demo

# Public demo: run after implementing the class API above.
b = BookMyShow()
b.add_show('S1', 'Dune', 'Screen 1', 5)
print(b.available_seats('S1'))

Starter code

class BookMyShow:

    def __init__(self):
        """Initialize the state described in the problem."""
        pass

    def add_show(self, show_id, movie, screen, total_seats):
        """Implement the return value and rules in the API contract."""
        pass

    def available_seats(self, show_id):
        """-> sorted list of free seat numbers ([] for an unknown show)"""
        pass

    def book(self, show_id, user_id, seat_numbers):
        """-> booking id (int, starting at 1), or None if any seat is taken/invalid or the show is unknown or the seat list is empty"""
        pass

    def cancel(self, booking_id):
        """-> True if the booking was active and is now cancelled, False otherwise"""
        pass

    def booking_details(self, booking_id):
        """-> {"show":, "user":, "seats": [...], "active": bool}, or None"""
        pass

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