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.)
这里返回一个vector，不能用int m[n]来定义数组。否则返回会出错could not convert ‘(int*)(& m)’ from ‘int*’ to ‘std::vector<int>’