_1357.java

package com.fishercoder.solutions;

import java.util.HashMap;
import java.util.Map;

/**
 * 1357. Apply Discount Every n Orders
 *
 * 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 1:
 * 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.
 * */
public class _1357 {
    public static class Solution1 {
        public static class Cashier {

            int customerCount;
            int n;
            Map<Integer, Integer> productsToPrices;
            int discount;

            public Cashier(int n, int discount, int[] products, int[] prices) {
                this.n = n;
                this.customerCount = 0;
                this.discount = discount;
                this.productsToPrices = new HashMap<>();
                for (int i = 0; i < products.length; i++) {
                    productsToPrices.put(products[i], prices[i]);
                }
            }

            public double getBill(int[] product, int[] amount) {
                double totalPrice = 0;
                for (int i = 0; i < product.length; i++) {
                    totalPrice += productsToPrices.get(product[i]) * amount[i];
                }
                if (customerCount + 1 == n) {
                    //apply discount
                    totalPrice *= (double) (100 - discount) / 100;
                    customerCount = 0;
                } else {
                    customerCount++;
                }
                return totalPrice;
            }
        }
    }
}