Product Except Self

题目

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.)

class Solution {
    public int[] productExceptSelf(int[] nums) {
        int[] ans = new int[nums.length];
        if(nums.length == 0) return ans;
        int curr_product = 1;
        ans[0] = 1;
        for(int i = 1; i < nums.length; i++) {
            ans[i] = ans[i-1] * nums[i - 1];
        }
        for(int j = nums.length - 1; j >= 0; j--) {
            ans[j] = curr_product * ans[j];
            curr_product = curr_product * nums[j];
        }
        return ans;
    }
}