LeetCode 830. 较大分组的位置

vector<vector<int>> largeGroupPositions(string s) {
	vector<vector<int>> res;
	for (size_t i = 0; i < s.size();) {
		size_t index = i;
		size_t count = 1;
		for (size_t j = i + 1; j < s.size() && s[j] == s[i]; j++)
			count++;
		if (count >= 3) {
			vector<int>vec;
			vec.push_back(i);
			vec.push_back(i+count-1);
			res.push_back(vec);
		}
		i = i+count;
	}
	return res;
}