leeetcode 238[medium]---Product of Array Except Self

Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].

Solve it without division and in O(n).

For example, given [1,2,3,4], return [24,12,8,6].

Follow up:
Could you solve it with constant space complexity? (Note: The output array does not count as extra space for the purpose of space complexity analysis.)

思路：题目不难理解，难在不能运用除法。借鉴别人的，用两个for循环积累每个element左右两边的数的乘积，最后相乘，得到每个因子除该数以外的其他所有的数的乘积。