238. 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.)

代码：

class Solution {public:    vector<int> productExceptSelf(vector<int>& nums) {        int n=nums.size();        int tmp=1;        vector<int>res(n);        for(int i=0;i<n;i++)         {                               res[i]=tmp;            tmp*=nums[i];        }         tmp=1;        for(int i=n-1;i>=0;i--)        {            res[i]*=tmp;            tmp*=nums[i];        }          return res;     }};