013-2006

MO640 - Multiple-choice question

Consider the following statements about a string s with n distinct characters:

I. For s, there are 1 + n(n+1)/2 possible substrings.
II. For s, there are 2ⁿ possible subsequences.
III. For s, there are n + 1 possible prefixes.

1. Only statement II is correct.
2. Statements I and II are correct.
3. Statements II and III are correct.
4. Statements I and III are correct.
5. None of the above

Original idea by: Pedro C. Feijão