Product of Array Except Self - Leetcode 238 - Arrays & Strings (Python)

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[@GregHogg]

Master Data Structures & Algorithms For FREE at AlgoMap.io!

[@shreehari2589]

The way you explain stuff is awesome, keep up the good work and please also upload hard questions too

[@aimaalakhume]

Thanks, I love this solution! It was really easy to follow and I appreciate the concise code. I also never knew the zip() function existed

[@arsheyajain7055]

Literally the only video that helped!!! Thank you

[@GregHogg]

Glad to hear it 😎

[@annas8308]

Hi Greg! What is the app you use to draw and teach us? I find it very easy to use and would like to take notes while viewing your videos.

[@GregHogg]

I use miro! It's really good for drawing:)

[@annas8308]

@@GregHogg Thank you, Greg!

[@jarodlatta6185]

I think you could get a constant time and space improvement by doing two passes through the array: first construct the product of all elements (unless they're 0), then iterate through again and divide the total by the current element. You do have go handle for 0s as a special case though, which might make it just as complex

[@kiattim2100]

You can't use division. That's the rule in leetcode 238

[@jarodlatta6185]

@@kiattim2100 ah okay, that makes sense

[@SpaceTalon]

Thanks!

[@GregHogg]

Very welcome :)

[@Sanjay-bx6xb]

bro how do you come up with this logic

[@GregHogg]

Sometimes I might have figured it out, sometimes I might have just learned it elsewhere.

[@arshiailaty]

Could you please let me know what you think of this solution? I should mention that there is a problem in the output when we have only one zero in numbers. The second if returns an array with all zeros.
import numpy
class Solution:
def productExceptSelf(self, nums: List[int]) -> List[int]:
ans = []
ind = numpy.where(nums == 0)[0]
if len(ind) > 1:
return [0]*len(ind)
if len(ind) == 1:
i = ind[0]
res = numpy.prod(nums[:i]) * numpy.prod(nums[i+1:])
ans = [0]*len(nums)
ans[i] = res
return ans
product = numpy.prod(nums)
ans = [product // num for num in nums]
return ans

[@rishishah835]

What's the need to import numpy, the product function? Also, we're not allowed to use division, otherwise we could just iterate once -- get the total product, and then iterate through just dividing by each value in nums (unless 0)