A Single-Letter Piece Seen Three Times

Medium

You are given a string text of lowercase English letters. Call a substring (a contiguous non-empty piece) single-letter if all its characters are the same, such as "kkk" or "q", but not "kq". Find the length of the longest single-letter substring that occurs in text at least three times. Occurrences may overlap: in "bbbb" the substring "bb" occurs three times, starting at positions 0, 1 and 2. If no single-letter substring occurs three times, return -1.

Example 1

text='xxxyxxyx' → 2

"x" occurs 6 times and "xx" exactly three times: twice inside "xxx" and once in the middle. "xxx" occurs only once, so the answer is 2.

Example 2

text='mnoonm' → -1

Each letter appears only twice, so no single-letter substring occurs three times.

Example 3

text='ttttttt' → 5

Constraints

3 ≤ len(text) ≤ 50
text consists of lowercase English letters

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Topics

Hash Table String Binary Search Counting Sliding Window

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Input

text='xxxyxxyx'

Expected

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