LeetCode 238 - Product of Array Except Self - 2023.10.06 solution

class Solution:
    def productExceptSelf(self, nums: List[int]) -> List[int]:
        """ Solution: Have one list of the products going from R->L.
        Then work through the list, just keeping a variable for
        the L->R product.
        Then, for each index, multiply the value at i in the R->L list
        with the variable storing the L->R product.
        """

        r_to_l = [None for n in nums]
        for i in range(len(nums)-1, -1, -1):
            if i == len(nums)-1:
                r_to_l[i] = 1
            else:
                r_to_l[i] = r_to_l[i+1] * nums[i+1]
        l_to_r = 1

        products = []
        for i in range(len(nums)):
            products.append(l_to_r * r_to_l[i])
            l_to_r *= nums[i]
        return products