LeetCode-in-All

238. Product of Array Except Self

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.)

Solution

class Solution:
    def productExceptSelf(self, nums: List[int]) -> List[int]:
        product = 1
        ans = [0] * len(nums)
        for num in nums:
            product *= num
        
        for i in range(len(nums)):
            if nums[i] != 0:
                ans[i] = product // nums[i]
            else:
                p = 1
                for j in range(len(nums)):
                    if j != i:
                        p *= nums[j]
                ans[i] = p
                
        return ans

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