1357.ApplyDiscountEverynOrders.py

"""
    There is a sale in a supermarket, there will be a discount every n customer.
    There are some products in the supermarket where the id of the i-th product 
    is products[i] and the price per unit of this product is prices[i].
    The system will count the number of customers and when the n-th customer 
    arrive he/she will have a discount on the bill. (i.e if the cost is x the 
    new cost is x - (discount * x) / 100). Then the system will start counting 
    customers again.
    The customer orders a certain amount of each product where product[i] is 
    the id of the i-th product the customer ordered and amount[i] is the number 
    of units the customer ordered of that product.

    Implement the Cashier class:
        - Cashier(int n, int discount, int[] products, int[] prices) Initializes 
          the object with n, the discount, the products and their prices.
        - double getBill(int[] product, int[] amount) returns the value of the 
          bill and apply the discount if needed. Answers within 10^-5 of the 
          actual value will be accepted as correct.

    Example:
    Input:
    ["Cashier","getBill","getBill","getBill","getBill","getBill","getBill","getBill"]
    [[3,50,[1,2,3,4,5,6,7],[100,200,300,400,300,200,100]],[[1,2],[1,2]],[[3,7],
    [10,10]],[[1,2,3,4,5,6,7],[1,1,1,1,1,1,1]],[[4],[10]],[[7,3],[10,10]],
    [[7,5,3,1,6,4,2],[10,10,10,9,9,9,7]],[[2,3,5],[5,3,2]]]

    Output:
    [null,500.0,4000.0,800.0,4000.0,4000.0,7350.0,2500.0]

    Explanation:
    Cashier cashier = new Cashier(3,50,[1,2,3,4,5,6,7],[100,200,300,400,300,200,100]);
    cashier.getBill([1,2],[1,2]);                        // return 500.0, 
                                                         // bill = 1 * 100 + 2 * 200 = 500.
    cashier.getBill([3,7],[10,10]);                      // return 4000.0
    cashier.getBill([1,2,3,4,5,6,7],[1,1,1,1,1,1,1]);    // return 800.0, The bill was 1600.0 but as this is the third customer, 
                                                         // he has a discount of 50% which means his bill is only 
                                                         // 1600 - 1600 * (50 / 100) = 800.
    cashier.getBill([4],[10]);                           // return 4000.0
    cashier.getBill([7,3],[10,10]);                      // return 4000.0
    cashier.getBill([7,5,3,1,6,4,2],[10,10,10,9,9,9,7]); // return 7350.0, 
                                                         // Bill was 14700.0 but as the system counted three more customers, he 
                                                         // will have a 50% discount and the bill becomes 7350.0
    cashier.getBill([2,3,5],[5,3,2]);                    // return 2500.0

    Constraints:
        - 1 <= n <= 10^4
        - 0 <= discount <= 100
        - 1 <= products.length <= 200
        - 1 <= products[i] <= 200
        - There are not repeated elements in the array products.
        - prices.length == products.length
        - 1 <= prices[i] <= 1000
        - 1 <= product.length <= products.length
        - product[i] exists in products.
        - amount.length == product.length
        - 1 <= amount[i] <= 1000
        - At most 1000 calls will be made to getBill.
        - Answers within 10^-5 of the actual value will be accepted as correct.
"""
#Difficulty: Medium
#25 / 25 test cases passed.
#Runtime: 780 ms
#Memory Usage: 21 MB

#Runtime: 780 ms, faster than 81.36% of Python3 online submissions for Apply Discount Every n Orders.
#Memory Usage: 21 MB, less than 90.91% of Python3 online submissions for Apply Discount Every n Orders.
    
class Cashier:

    def __init__(self, n: int, discount: int, products: List[int], prices: List[int]):
        self.count = 0
        self.n = n
        self.discount = discount
        self.products = {}
        for i in range(len(products)):
            self.products[products[i]] = prices[i]

    def getBill(self, product: List[int], amount: List[int]) -> float:
        bill = 0
        self.count += 1
        for i in range(len(product)):
            bill += amount[i] * self.products[product[i]]
        if self.count == self.n:
            self.count = 0
            bill -= bill * self.discount / 100
        return bill


# Your Cashier object will be instantiated and called as such:
# obj = Cashier(n, discount, products, prices)
# param_1 = obj.getBill(product,amount)