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


Input:  [1,2,3,4]
Output: [24,12,8,6]
Constraint: It's guaranteed that the product of the elements of any prefix or suffix of the array (including the whole array) fits in a 32 bit integer.

Note: Please solve it without division and in O(n).

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

func productExceptSelf(nums []int) []int {
    lenN := len(nums)
    result := make([]int, lenN)
    preLeft := 1 
    for i:= 0; i < lenN; i++ {
        result[i] = preLeft
        preLeft *= nums[i]
    preRight := 1
    for i:= lenN-1; i >= 0; i-- {
        result[i] *= preRight
        preRight *= nums[i]
    return result