Check if string has all the letters of the alphabet

Question

What would be the best logic to check all the letters in a given string.

If all the 26 letters are available in the provided string, I want to check that and perform

Answer 1

I'd go for a bitmap. If you increment a counter each time you set an entry in the bitmap to 1, you can early return as soon as you've seen all the letters. I hope this is not for enforcing password requirements.