1955. Count Number of Special Subsequences

A sequence is special if it consists of a positive number of 0s, followed by a positive number of 1s, then a positive number of 2s. - For example, [0,1,2] and [0,0,1,1,1,2] are special. - In contrast, [2,1,0], [1], and [0,1,2,0] are not special. Given an array nums (consisting of only integers 0, 1, and 2), return the number of different subsequences that are special. Since the answer may be ve