1352.ProductoftheLastKNumbers(Revisited).py

"""
    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
"""
#Difficulty: Medium
#33 / 33 test cases passed.
#Runtime: 284 ms
#Memory Usage: 28.9 MB

#Runtime: 284 ms, faster than 92.12% of Python3 online submissions for Product of the Last K Numbers.
#Memory Usage: 28.9 MB, less than 86.36% of Python3 online submissions for Product of the Last K Numbers.

class ProductOfNumbers:

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

    def add(self, num: int) -> None:
        if num == 0:
            self.array = [1]
        else:
            self.array.append(num)
            self.array[-1] *= self.array[-2]

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


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