[Solved] 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].

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Question

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 Solution

class Solution:
    def productExceptSelf(self, nums: List[int]) -> List[int]:
        p = 1
        n = len(nums)
        out = []
        for i in range(n):
            out.append(p)
            p = p*nums[i]
        print(out)
        p=1
        for i in range(n-1,-1,-1):
            out[i] = out[i]*p
            p = p*nums[i]
        return(out)

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