[Leetcode/파이썬] 238. Product of Array Except Self

Product of Array Except Self

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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 <= 105
• -30 <= nums[i] <= 30
• The input is generated such that answer[i] is guaranteed to fit in a 32-bit integer.

 

Follow up: Can you solve the problem in O(1) extra space complexity? (The output array does not count as extra space for space complexity analysis.)

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

        left = 1
        right = 1

        res = [1] * n

        for i in range(n) :
            res[i] *= left
            left *= nums[i]

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

        return res