Create apply-discount-every-n-orders.cpp

Author: kamyu104

C++/apply-discount-every-n-orders.cpp

@@ -0,0 +1,31 @@
+// Time:  ctor:    O(m), m is the number of all products
+//        getBill: O(p), p is the number of products to bill
+// Space: O(m)
+
+class Cashier {
+public:
+    Cashier(int n, int discount, vector<int>& products, vector<int>& prices)
+      : n_{n}
+      , discount_{discount}
+      , curr_{0}
+    {
+        for (int i = 0; i < products.size(); ++i) {
+            lookup_[products[i]] = prices[i];
+        }
+    }
+    
+    double getBill(vector<int> product, vector<int> amount) {
+        curr_ = (curr_ + 1) % n_;
+        double result = 0.0;
+        for (int i = 0; i < product.size(); ++i) {
+            result += lookup_[product[i]] * amount[i];
+        }
+        return curr_ == 0 ? result * (1.0 - discount_ / 100.0) : result;
+    }
+
+private:
+    int n_;
+    int discount_;
+    int curr_;
+    unordered_map<int, int> lookup_;
+};