Given an array of **distinct** integers `nums`

and a target integer `target`

, return *the number of possible combinations that add up to* `target`

.

The answer is **guaranteed** to fit in a **32-bit** integer.

**Example 1:**

Input:nums = [1,2,3], target = 4Output:7Explanation:The possible combination ways are: (1, 1, 1, 1) (1, 1, 2) (1, 2, 1) (1, 3) (2, 1, 1) (2, 2) (3, 1) Note that different sequences are counted as different combinations.

**Example 2:**

Input:nums = [9], target = 3Output:0

**Constraints:**

`1 <= nums.length <= 200`

`1 <= nums[i] <= 1000`

- All the elements of
`nums`

are**unique**. `1 <= target <= 1000`

**Follow up:** What if negative numbers are allowed in the given array? How does it change the problem? What limitation we need to add to the question to allow negative numbers?

class Solution {
public int combinationSum4(int[] nums, int target) {
}
}