Here's a toy problem. Given a corpus of phone numbers for different countries determine a most prevalent display format in each country and use it to re-format an arbitrary phone number for its country. For example, if most US numbers in our data corpus are written like
xxx-xxx-xxxx then the string
(206) 1234567 should be converted to
For simplicity, let's assume that all numbers are local so we don't have to deal with complexity of international prefixes.