[LeetCode] 0238. Product of Array Except Self

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Product of Array Except Self

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內容目錄

Medium

 

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 product of any prefix or suffix of nums 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.)

Python

				
					# time complexity: O(n)
# space complexity: O(n)
from typing import List


class Solution:
    def productExceptSelf(self, nums: List[int]) -> List[int]:
        length = len(nums)
        lList, rList = [1]*length, [1]*length
        lList[0], rList[length - 1] = 1, 1
        for i in range(1, length):
            lList[i] = lList[i-1] * nums[i-1]
        for i in reversed(range(length-1)):
            rList[i] = rList[i+1] * nums[i+1]

        for i in range(length):
            lList[i] *= rList[i]

        return lList


Arrays = [-1, 1, 0, -3, 3]

print(Solution().productExceptSelf(Arrays))

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