Product of Array Except Self

Given an integer array nums, return an array answer such that answer[i] is equal to the product of all the elements of nums except nums[i].

The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer.

You must write an algorithm that runs in O(n) time and without using the division operation.

Example 1:

Input: nums = [1,2,3,4]
Output: [24,12,8,6]

Example 2:

Input: nums = [-1,1,0,-3,3]
Output: [0,0,9,0,0]

Constraints:

• 2 <= nums.length <= 10<sup>5</sup>

• -30 <= nums[i] <= 30

• The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer.

Solution:

class Solution:
    def productExceptSelf(self, nums: List[int]) -> List[int]:
        res = [1] * (len(nums))

        for i in range(1, len(nums)):
            res[i] = res[i-1] * nums[i-1]


        postfix = 1
        for i in range(len(nums) - 1, -1, -1):
            res[i] *= postfix
            postfix *= nums[i]

        return res