Please solve the programming task below using a self-contained code snippet in a markdown code block.

Given an array of distinct integers nums and a target integer target, return the number of possible combinations that add up to target.
The test cases are generated so that the answer can fit in a 32-bit integer.
 
Please complete the following python code precisely:
```python
class Solution:
    def combinationSum4(self, nums: List[int], target: int) -> int:
```