LeetCode 1357. Apply Discount Every n Orders

, , , , ,

Question

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.

You can check the official leetcode website

Example

1
2
3
4
5
6
7
8
9
10
11
12
13
14
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

Solution

It needs you to read more carefully, and we only need to keep tracking the relationship between productID and Price. Also, we need to pay attention when we give the low price (the value of n).

Code

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
// time: O(n), space:O(n)
		public int count;
    public int n;
    public int dis;
    public HashMap<Integer, Integer> map;
    public Cashier(int n, int discount, int[] products, int[] prices) {
        count = 0;
        this.n = n;
        dis = discount;
        map = new HashMap<>();
        for (int i = 0; i < products.length; i++) {
            map.put(products[i], prices[i]);
        }
    }
    
    public double getBill(int[] product, int[] amount) {
        count++;
        double res = 0;
        for (int i = 0; i < product.length; i++) {
            res += map.get(product[i]) * amount[i];
        }
        if (count % n == 0) return res - res * (dis) / 100;
        return res;
    }