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

A decimal number is called deci-binary if each of its digits is either 0 or 1 without any leading zeros. For example, 101 and 1100 are deci-binary, while 112 and 3001 are not.
Given a string n that represents a positive decimal integer, return the minimum number of positive deci-binary numbers needed so that they sum up to n.
 
Please complete the following python code precisely:
```python
class Solution:
    def minPartitions(self, n: str) -> int:
```