E-commerce Platform Backend
HardProblem Description
Design a backend-like model with User (Customer, Admin), a Product hierarchy, Order, and PaymentGateway.
Apply composition for cart logic. Use a Factory to create orders, and ensure extensibility for new product categories or payment methods.
Handle edge cases like refunds and inventory.
OOP Focus: Full system design with OOP principles.
Note: This is statement-only in the current Practice version; stdout should be empty.
Input & Output Format
INPUT:
Two lines. First line: space-separated numbers for vector a.
Second line: space-separated numbers for vector b.
Second line: space-separated numbers for vector b.
OUTPUT:
A single number (the dot product).
Example
Input:
1 2 3
4 5 6
4 5 6
Output:
32
Explanation: 1×4 + 2×5 + 3×6 = 4 + 10 + 18 = 32
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Output
Run or submit to see output.