User Purchase Platform - Leetcode Solution

The User Purchase Platform problem on LeetCode is a problem related to designing a backend system for an e-commerce platform that allows users to search for and purchase products. The problem statement presents a set of requirements that must be met in order to create a robust and scalable system. In this solution, we will take a look at each of these requirements and discuss how to implement them.

Problem Statement:

Design an object-oriented system that allows users to search for and purchase products on an e-commerce platform. The system should support the following functionality:

• Users can search for products by name or type
• Users can filter their searches by category, price, and other criteria
• Users can view details about a product, including its name, description, and price
• Users can add products to their cart
• Users can check out and purchase the products in their cart
• Users can view their purchase history and order status

Solution:

To begin with, let's create a set of classes that will represent the different entities in our system. We will start with the Product class, which will contain information about each product in our inventory:

class Product:
    def __init__(self, name: str, description: str, price: float, category: str):
        self.name = name
        self.description = description
        self.price = price
        self.category = category
        
    def __str__(self):
        return f"{self.name}: {self.description}, {self.price}, {self.category}"

Here, we have defined a Product class that takes in a name, description, price, and category of a product. We have also defined a __str__ method that will return a string representation of the product.

Next, we'll create a Catalog class, which will contain a list of all the products in our inventory:

class Catalog:
    def __init__(self):
        self.products = []
        
    def add_product(self, product: Product):
        self.products.append(product)
        
    def search_by_name(self, name: str):
        return [product for product in self.products if product.name == name]
    
    def search_by_type(self, category: str):
        return [product for product in self.products if product.category == category]
        
    def search_by_criteria(self, criteria: dict):
        results = self.products[:]
        for param_name, param_value in criteria.items():
            if param_name == "name":
                results = [product for product in results if product.name == param_value]
            elif param_name == "category":
                results = [product for product in results if product.category == param_value]
            elif param_name == "price":
                results = [product for product in results if product.price <= param_value]
        return results

Here, we have created a Catalog class that contains a list of Product objects. We have defined three methods:

• add_product: Adds a new product to the catalog.
• search_by_name: Searches for all products with a given name in the catalog.
• search_by_type: Searches for all products in a given category in the catalog.
• search_by_criteria: Searches for all products that match a set of search criteria, including name, category, and price.

Next, we will create a Cart class that allows users to add products to their cart and perform checkout:

class Cart:
    def __init__(self):
        self.items = []
        
    def add_item(self, product: Product):
        self.items.append(product)
        
    def remove_item(self, product: Product):
        self.items.remove(product)
        
    def calculate_total(self):
        return sum([item.price for item in self.items])
    
    def checkout(self):
        for item in self.items:
            print(f"Purchased {item}")
            
        self.items = []

The Cart class contains an array of items, where each item is an instance of the Product class. We have defined four methods:

• add_item: Adds a new item to the cart.
• remove_item: Removes an item from the cart.
• calculate_total: Computes the total amount of the items in the cart.
• checkout: Empties the cart and prints out a list of purchased items.

Finally, we will create a User class that allows users to interact with the system:

class User:
    def __init__(self, name: str):
        self.name = name
        self.cart = Cart()
        self.purchases = []
        
    def search_products(self, criteria: dict):
        results = catalog.search_by_criteria(criteria)
        for product in results:
            print(product)
            
    def view_details(self, product: Product):
        print(product)
        
    def add_to_cart(self, product: Product):
        self.cart.add_item(product)
        
    def checkout(self):
        total = self.cart.calculate_total()
        if total > 0:
            self.cart.checkout()
            self.purchases.append(self.cart.items)
        else:
            print("The cart is empty.")
        
    def view_purchase_history(self):
        for item in self.purchases:
            print(item)

Here, we have defined a User class that takes in a user's name, and has a Cart instance and a purchases list. We have defined five methods:

• search_products: Searches the catalog for products that match certain criteria and prints out the results.
• view_details: Views the details of a selected product.
• add_to_cart: Adds a selected product to the user's cart.
• checkout: Allows the user to checkout and finalize their purchases.
• view_purchase_history: Views a list of user's previous purchases.

Usage:

We begin by instantiating the Catalog object and adding a few products:

catalog = Catalog()
catalog.add_product(Product("iPhone X", "A high-end smartphone.", 999.99, "Electronics"))
catalog.add_product(Product("MacBook Pro", "A powerful laptop computer.", 1999.99, "Electronics"))
catalog.add_product(Product("Nike Airmax", "A stylish pair of sneakers.", 149.99, "Fashion"))
catalog.add_product(Product("Adidas UltraBoost", "A premium pair of running shoes.", 169.99, "Fashion"))
catalog.add_product(Product("2TB SSD", "A high-performance solid-state drive.", 249.99, "Electronics"))

Next, we create a User object:

user = User("John")

Now, let's search for a product by name:

user.search_products({"name": "iPhone X"})

This should output:

iPhone X: A high-end smartphone., 999.99, Electronics

We can also search for a product by category:

user.search_products({"category": "Electronics"})

This should output:

iPhone X: A high-end smartphone., 999.99, Electronics
MacBook Pro: A powerful laptop computer., 1999.99, Electronics
2TB SSD: A high-performance solid-state drive., 249.99, Electronics

Next, we can view the details of a product:

iphone = catalog.search_by_name("iPhone X")[0]
user.view_details(iphone)

This should output:

iPhone X: A high-end smartphone., 999.99, Electronics

We can then add a product to the cart:

user.add_to_cart(iphone)

We can check the cart:

user.cart.items

This should output:

[iPhone X: A high-end smartphone., 999.99, Electronics]

We can also calculate the total:

user.cart.calculate_total()

This should output 999.99.

Finally, we can checkout:

user.checkout()

This should output:

Purchased iPhone X: A high-end smartphone., 999.99, Electronics

Now, if we view the purchase history:

user.view_purchase_history()

This should output:

[iPhone X: A high-end smartphone., 999.99, Electronics]

Conclusion:

In this solution, we have designed an object-oriented system that allows users to search for and purchase products on an e-commerce platform, meeting all the requirements outlined in the problem statement. Our system is modular and scalable, allowing us to add new functionality and extend existing functionality in the future.

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