When needed a list of unique divisors (2nd solutinon [here](https://leetcode.com/problems/split-the-array-to-make-coprime-products/solutions/3261267/1984-ms/)), creating (and destructing) a 2D array in `prime_division` is unnecessary. Creating an 1D array should be less expensive.
When needed a list of unique divisors (2nd solutinon here), creating (and destructing) a 2D array in
prime_divisionis unnecessary.Creating an 1D array should be less expensive.