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Product of Array Except Self

Problem Statement​

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.

Leetcode Link

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.

Code​

Python Code
class Solution(object):
    def productExceptSelf(self, nums):
        p,prod=[1]*len(nums),1
        for i in xrange(1,len(nums)):
            p[i]=p[i-1]*nums[i-1]

        for i in reversed(xrange(len(nums)-1)):
            prod=nums[i+1]*prod
            p[i]=p[i]*prod
        return p