Problem Statement  
You will be given a list of patterns. Each pattern will contain only digits ('0''9'), question marks ('?'), and may potentially begin or end (but not both) with a hyphen (''). You must return the number of strings of length len that match all of the patterns. A digit must be matched with the same digit. A question mark can be matched with any digit. If the pattern ends with a hyphen, the pattern is describing a prefix. Similarly, if the pattern begins with a hyphen it describes a suffix. If there are no hyphens, the matched string must have the same length as the pattern. Said differently, a hyphen matches 0 or more digits.  
Definition  
 
Constraints  
  patterns will contain between 1 and 50 elements, inclusive.  
  Each element of patterns will contain between 1 and 50 characters, inclusive.  
  Each character in patterns will be a digit ('0''9'), a question mark ('?'), or a hyphen ('');  
  Each element of patterns will contain at most 1 hyphen, and it must occur at the beginning or the end of the element.  
  len will be between 1 and 50, inclusive.  
  The return value will be between 0 and 1,000,000,000, inclusive.  
  No element of patterns will be "" (quotes for clarity).  
Examples  
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