【leetcode】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.)

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class Solution {public:    vector<int> productExceptSelf(vector<int>& nums) {        vector<int> result;        int tmp = 1;        result.push_back(tmp);        for (vector<int>::const_iterator it = nums.begin(); it != nums.end() - 1; ++it)        {            tmp *= (*it);            result.push_back(tmp);        }        tmp = 1;        vector<int>::iterator it_result = result.end() - 2;        for (vector<int>::const_iterator it = nums.end() - 1; it != nums.begin(); --it)        {            tmp *= (*it);            (*it_result) *= tmp;            --it_result;        }                return result;    }};

Personal Note:

遍历nums两次，第一次正序，计算索引i之前各数乘积并存入result，第二次反序，计算索引i之后各数乘积并与之前result相乘，得到最终result。