Write count_sentences(text) that counts the sentences in a piece of text. A sentence ends at a run of one or more terminator characters ., !, ? (so "Really?!" and "Wait..." each end one sentence). Text after the last terminator counts as one more sentence if it contains any non-whitespace character. A stretch that contains only whitespace between terminators is not a sentence.
Examples
Input: text = "Hello there. How are you?! Fine..."
Output: 3
Input: text = "no ending"
Output: 1
Input: text = "..."
Output: 0
Constraints
0 <= len(text) <= 10**5, printable ASCII and whitespace- Target: O(n) time
Goals
- Recognise sentence terminators
- Treat a run of terminators as one boundary
- Track whether the current sentence has any content