Product of Array Except Self leetcode

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].

给出一个数组nums=[a1, a2, a3, a4]。 
想在O(n)时间复杂度完成最终的数组输出，res=[a2*a3*a4, a1*a3*a4, a1*a2*a4, a2*a3*a4]。

可以构造两个数组相乘：

1. [1, a1, a1*a2, a1*a2*a3]
2. [a2*a3*a4, a3*a4, a4, 1]

public class Solution {
    public int[] productExceptSelf(int[] nums) {
        int[] res = new int[nums.length];
        int [] tem = new int[nums.length];
        res[0] = 1;
        for (int i = 1; i < nums.length; i++) {
            res[i] = res[i - 1] * nums[i - 1];
        }
        tem[nums.length - 1] = 1;
        for (int i = nums.length - 2; i >= 0; i--) {
            tem[i] = tem[i + 1] * nums[i + 1];
        }
        for (int i = 0; i < nums.length; i++) {
            res[i] = res[i] * tem[i];
        }
        return res;
    }
}