Validate German cellphone number

FO-5 Validate a German cellphone number

Validate if a cellphone number has the typical German number structure.

The number should start with 0049, if not it should start with 0. After that, an optional space could follow, and then 11 digits from 0 to 9. In between these 11 digits the user has the opportunity to put an optional space wherever he wants.

Accepted data: 

1. 0049 15770452536

2. 015770452536

3. 00491577 0452536

4. 0157 74 525 36

Hint: Check the grouping () characters expression again. Try not to write 11 times the same pattern for every character. What if we are talking about 50 or 500 characters?