Cab Booking

medium · nearest-neighbour matching, ride lifecycle, fare

Brief-reported interview attribution (unverified): Uber, Lyft, Ola

Design a ride-hailing system. Drivers and riders have (x, y) coordinates. request_ride matches the nearest available driver to the rider (Euclidean distance; ties break to the lowest driver id). A ride moves through "requested" → "ongoing" → "completed" (or "cancelled" from "requested" only). Fare is $5 + $2 × distance(pickup, destination), rounded to 2 decimals. On completion the driver becomes available at the destination.

class RideHailing:
    def __init__(self):
    def add_driver(self, driver_id, x, y):
    def add_rider(self, rider_id, x, y):
    def request_ride(self, rider_id, dest_x, dest_y):
        # -> ride id (int, starting at 1), or None if the rider is unknown or
        #    no driver is available
    def start_ride(self, ride_id):
        # -> True if the ride was "requested" and is now "ongoing", False otherwise
    def complete_ride(self, ride_id):
        # -> fare (float) if the ride was "ongoing", None otherwise
    def cancel_ride(self, ride_id):
        # -> True if the ride was "requested" and is now cancelled, False otherwise
    def ride_status(self, ride_id):
        # -> "requested" | "ongoing" | "completed" | "cancelled" | "unknown"
    def driver_location(self, driver_id):
        # -> (x, y), or None for an unknown driver

Rules. A driver is busy from the moment a ride is requested until it is completed or cancelled; a busy driver is never matched. Cancelling frees the driver at their current location (unchanged). Fares use the pickup location recorded at request time.

Money units: fares are dollars, rounded to two decimal places; a distance of 4 returns 13.0.

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.
r = RideHailing()
r.add_driver('D1', 0, 0)
r.add_driver('D2', 10, 0)
r.add_rider('R1', 3, 0)
print(r.request_ride('R1', 3, 4))
print(r.ride_status(1))

Starter code

class RideHailing:

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

    def add_driver(self, driver_id, x, y):
        """Implement the return value and rules in the API contract."""
        pass

    def add_rider(self, rider_id, x, y):
        """Implement the return value and rules in the API contract."""
        pass

    def request_ride(self, rider_id, dest_x, dest_y):
        """-> ride id (int, starting at 1), or None if the rider is unknown or no driver is available"""
        pass

    def start_ride(self, ride_id):
        """-> True if the ride was "requested" and is now "ongoing", False otherwise"""
        pass

    def complete_ride(self, ride_id):
        """-> fare (float) if the ride was "ongoing", None otherwise"""
        pass

    def cancel_ride(self, ride_id):
        """-> True if the ride was "requested" and is now cancelled, False otherwise"""
        pass

    def ride_status(self, ride_id):
        '''-> "requested" | "ongoing" | "completed" | "cancelled" | "unknown"'''
        pass

    def driver_location(self, driver_id):
        """-> (x, y), or None for an unknown driver"""
        pass

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