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.)

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该题没有想出来！太不应该了
思路：
res[i] = forward[i] * backword[i]
forword[i]:i之前的所有数乘积
backword[i]:i后的所有数乘积

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