参考代码:
class Solution: def twitchWords(self, str): n = len(str) c = str[0] left = 0 ans = [] for i in range(n): if str[i] != c: if i - left >= 3: ans.append(left, i -1) c = str[i] left = i if n - left >= 3: ans.append([left, n - 1]) return ans