Product of the Last K Numbers

Author: anantkaushik

1352-product-of-the-last-k-numbers.py

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+"""
+Problem Link: https://leetcode.com/problems/product-of-the-last-k-numbers/
+
+Implement the class ProductOfNumbers that supports two methods:
+1. add(int num)
+Adds the number num to the back of the current list of numbers.
+2. getProduct(int k)
+
+Returns the product of the last k numbers in the current list.
+You can assume that always the current list has at least k numbers.
+At any time, the product of any contiguous sequence of numbers will fit 
+into a single 32-bit integer without overflowing.
+
+Example:
+
+Input
+["ProductOfNumbers","add","add","add","add","add","getProduct","getProduct","getProduct",
+"add","getProduct"]
+[[],[3],[0],[2],[5],[4],[2],[3],[4],[8],[2]]
+Output
+[null,null,null,null,null,null,20,40,0,null,32]
+
+Explanation
+ProductOfNumbers productOfNumbers = new ProductOfNumbers();
+productOfNumbers.add(3);        // [3]
+productOfNumbers.add(0);        // [3,0]
+productOfNumbers.add(2);        // [3,0,2]
+productOfNumbers.add(5);        // [3,0,2,5]
+productOfNumbers.add(4);        // [3,0,2,5,4]
+productOfNumbers.getProduct(2); // return 20. The product of the last 2 numbers is 5 * 4 = 20
+productOfNumbers.getProduct(3); // return 40. The product of the last 3 numbers is 2 * 5 * 4 = 40
+productOfNumbers.getProduct(4); // return 0. The product of the last 4 numbers is 0 * 2 * 5 * 4 = 0
+productOfNumbers.add(8);        // [3,0,2,5,4,8]
+productOfNumbers.getProduct(2); // return 32. The product of the last 2 numbers is 4 * 8 = 32 
+ 
+Constraints:
+There will be at most 40000 operations considering both add and getProduct.
+0 <= num <= 100
+1 <= k <= 40000
+"""
+class ProductOfNumbers:
+
+    def __init__(self):
+        self.product = [1]
+
+    def add(self, num: int) -> None:
+        if num == 0:
+          self.product = [1]
+        else:
+          self.product.append(self.product[-1]*num)  
+        
+    def getProduct(self, k: int) -> int:
+        if k >= len(self.product):
+          return 0
+        return self.product[-1] // self.product[-k-1]
+
+
+# Your ProductOfNumbers object will be instantiated and called as such:
+# obj = ProductOfNumbers()
+# obj.add(num)
+# param_2 = obj.getProduct(k)