Product of Array Except Self

Description

Given an array nums of n integers where n > 1, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].

Example:

Input: [1,2,3,4]

Output: [24,12,8,6]

Constraint: It's guaranteed that the product of the elements of any prefix or suffix of the array (including the whole array) fits in a 32 bit integer.

Note: Please solve it without division and in O(n).

Follow up: Could you solve it with constant space complexity? (The output array does not count as extra space for the purpose of space complexity analysis.)

Code

class Solution {
    public int[] productExceptSelf(int[] nums) {
        int sum = 1;
        int zeroNum = 0;
        int[] output = new int[nums.length];
        for (int i = 0; i < nums.length; i++) {
            if (nums[i] != 0) {
                sum *= nums[i];                
            } else {
                zeroNum++;
            }
        }
        if (zeroNum >= 2) return output;
        for (int i = 0; i < nums.length; i++) {
            if (zeroNum == 0) {
                output[i] = sum / nums[i];
            } else {
                if (nums[i] == 0) output[i] = sum;
                else output[i] = 0;
            }
        }
        return output;
    }
}