2025-08-01 05:13:47 +0000 UTC

class Solution:
    def largeGroupPositions(self, s: str) -> List[List[int]]:
        res = []
        start = 0
        prev = s[0]
        for i, char in enumerate(itertools.chain(s[1:], " "), 1):
            if char == prev:
                continue
            if i - 1 - start >= 2:
                res.append((start, i - 1))
            start = i
            prev = char
        return res