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.prefix_prod = [1]

    def add(self, num: int) -> None:
        if num == 0:
            self.prefix_prod = [0] * len(self.prefix_prod) + [1]
        else:
            self.prefix_prod.append(self.prefix_prod[-1] * num)

    def getProduct(self, k: int) -> int:
        n = len(self.prefix_prod)
        if self.prefix_prod[n - k - 1] == 0:
            return 0
        else:
            return self.prefix_prod[n - 1] // self.prefix_prod[n - k - 1]


# Your ProductOfNumbers object will be instantiated and called as such:
# obj = ProductOfNumbers()
# obj.add(num)
# param_2 = obj.getProduct(k)

class ProductOfNumbers:

    def __init__(self):
        self.prefix_prod = [1]

    def add(self, num: int) -> None:
        if num == 0:
            self.prefix_prod = [0] * len(self.prefix_prod) + [1]
        else:
            self.prefix_prod.append(self.prefix_prod[-1] * num)

    def getProduct(self, k: int) -> int:
        n = len(self.prefix_prod)
        if self.prefix_prod[n - k - 1] == 0:
            return 0
        else:
            return self.prefix_prod[n - 1] // self.prefix_prod[n - k - 1]


# Your ProductOfNumbers object will be instantiated and called as such:
# obj = ProductOfNumbers()
# obj.add(num)
# param_2 = obj.getProduct(k)
