In a string s of lowercase letters, these letters form consecutive groups of the same character. For example, a string like s = "abbxxxxzyy" has the groups "a", "bb", "xxxx", "z", and "yy". A group is identified by an interval [start, end], where start and end denote the start and end indices (inclusive) of the group. In the above example, "xxxx" has the interval [3,6]. A group is considered large if it has 3 or more characters. Return the intervals of every large group sorted in increasing order by start index. Example 1: Input: s = "abbxxxxzzy" Output: [[3,6]] Explanation: "xxxx" is the only large group with start index 3 and end index 6. Example 2: Input: s = "abc" Output: [] Explanation: We have groups "a", "b", and "c", none of which are large groups. Example 3: Input: s = "abcdddeeeeaabbbcd" Output: [[3,5],[6,9],[12,14]] Explanation: The large groups are "ddd", "eeee", and "bbb". Example 4: Input: s = "aba" Output: [] Constraints: 1 <= s.length <= 1000 s contains lower-case English letters only.