product-of-array-except-self.py

# https://leetcode.com/problems/product-of-array-except-self/description/
class Solution:
    def productExceptSelf(self, nums):
        forward_mul = []
        backward_mul = []

        cumulator = 1
        for num in nums:
            product = num * cumulator
            cumulator = product
            forward_mul.append(product)

        cumulator = 1
        for num in reversed(nums):
            product = num * cumulator
            cumulator = product
            backward_mul.append(product)
        backward_mul.reverse()

        for i in range(len(nums)):
            forward_result = forward_mul[i - 1] if i - 1 >= 0 else 1
            backward_result = backward_mul[i + 1] if i + 1 < len(nums) else 1
            nums[i] = forward_result * backward_result

        return nums[i]

    def productExceptSelfFollowUp(self, nums):
        result = []
        cumulator = 1
        for i in range(len(nums)):
            if i == 0:
                result.append(1)
            else:
                result.append(cumulator)
            cumulator *= nums[i]
        print(result)
        cumulator = 1
        for i in range(len(nums) - 1, -1, -1):
            result[i] *= cumulator
            cumulator *= nums[i]
        print(result)
        return result


# s = Solution()
Solution().productExceptSelf([1, 2, 3, 4])