0830. Positions of Large Groups

https://leetcode.com/problems/positions-of-large-groups

Description

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.

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