Leetcode #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 ofnums 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.)

      题目很有意思，要求在不用除法的情况下时间复杂度仍为O（n），这确实需要动点脑筋。代码如下：

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