71-consecutive-letters.md

Problem:

In this Kata, we will check if a string contains consecutive letters as they appear in the English alphabet and if each letter occurs only once.

For example: 
solve("abc") = True, because it contains a,b,c
solve("abd") = False, because a, b, d are not consecutive.
solve("dabc") = True, because it contains a, b, c, d
solve("abbc") = False, because b does not occur once.
solve("v") = True

All inputs will be lowercase letters.

More examples in test cases. Good luck!

Solution