> For the complete documentation index, see [llms.txt](https://jaywin.gitbook.io/leetcode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://jaywin.gitbook.io/leetcode/solutions/0830-positions-of-large-groups.md).

# 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.

## ac

```java
```