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 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.)

一刷
题解：不能用除法
先左边连乘
让res[I] = nums[0]...nums[I-1]
然后再右边连乘
res[I]= nums[I+1]..*nums[n]

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