Trip Fare Calculator

Description

Company: Uber

Problem Statement

Implement Uber's fare calculation engine. Given the parameters of a completed trip, compute the total fare charged to the rider.

Fare Formula

fare = max(
    base_fare + (per_mile_rate * miles) + (per_minute_rate * minutes) + tolls + booking_fee,
    minimum_fare
)

final_fare = fare * surge_multiplier

The function must handle multiple product types (UberX, UberXL, Uber Black) with different rate cards.

Function Signature

@dataclass
class RateCard:
    base_fare: int          # cents
    per_mile_rate: int      # cents per mile
    per_minute_rate: int    # cents per minute
    booking_fee: int        # cents
    minimum_fare: int       # cents

@dataclass
class Trip:
    distance_miles: float
    duration_minutes: float
    tolls_cents: int
    surge_multiplier: float
    rate_card: RateCard

def calculate_fare(trip: Trip) -> dict:
    """
    Returns:
        {
            "base_component": int,      # base_fare in cents
            "distance_component": int,  # per_mile_rate * miles in cents
            "time_component": int,      # per_minute_rate * minutes in cents
            "tolls": int,               # tolls in cents
            "booking_fee": int,         # booking fee in cents
            "subtotal": int,            # sum before surge, with minimum applied
            "surge_multiplier": float,
            "total": int                # final fare in cents (rounded to nearest cent)
        }
    """

Examples

Example 1: Standard trip

rate_card = RateCard(
    base_fare=200, per_mile_rate=150, per_minute_rate=25,
    booking_fee=250, minimum_fare=800
)
trip = Trip(
    distance_miles=5.2, duration_minutes=18.0,
    tolls_cents=0, surge_multiplier=1.0, rate_card=rate_card
)

base_component = 200
distance_component = 150 * 5.2 = 780
time_component = 25 * 18 = 450
tolls = 0
booking_fee = 250
raw_subtotal = 200 + 780 + 450 + 0 + 250 = 1680
subtotal = max(1680, 800) = 1680
total = round(1680 * 1.0) = 1680

Output: {"base_component": 200, "distance_component": 780, "time_component": 450,
         "tolls": 0, "booking_fee": 250, "subtotal": 1680,
         "surge_multiplier": 1.0, "total": 1680}

Example 2: Minimum fare kicks in

rate_card = RateCard(
    base_fare=200, per_mile_rate=150, per_minute_rate=25,
    booking_fee=250, minimum_fare=800
)
trip = Trip(
    distance_miles=0.3, duration_minutes=2.0,
    tolls_cents=0, surge_multiplier=1.0, rate_card=rate_card
)

raw_subtotal = 200 + 45 + 50 + 0 + 250 = 545
subtotal = max(545, 800) = 800
total = 800

Example 3: Surge pricing

rate_card = RateCard(
    base_fare=200, per_mile_rate=150, per_minute_rate=25,
    booking_fee=250, minimum_fare=800
)
trip = Trip(
    distance_miles=5.2, duration_minutes=18.0,
    tolls_cents=350, surge_multiplier=1.75, rate_card=rate_card
)

subtotal = 200 + 780 + 450 + 350 + 250 = 2030
total = round(2030 * 1.75) = 3553

Constraints

• All monetary values are in cents (integers) to avoid floating-point errors
• 0 < distance_miles <= 500
• 0 < duration_minutes <= 600
• 0 <= tolls_cents <= 10000
• 1.0 <= surge_multiplier <= 5.0
• distance_component and time_component should be rounded to nearest cent before summing

Edge Cases

• Very short trip triggers minimum fare
• Surge on minimum fare (minimum fare is also surged)
• Zero tolls
• Extremely long trip (airport rides)
• Rate card with 0 base fare (some markets)

Complexity Target

• Time: O(1)
• Space: O(1)