# 1992. Find All Groups of Farmland

https://leetcode.com/problems/find-all-groups-of-farmland

## Description

You are given a **0-indexed** `m x n` binary matrix `land` where a `0` represents a hectare of forested land and a `1` represents a hectare of farmland.

To keep the land organized, there are designated rectangular areas of hectares that consist **entirely** of farmland. These rectangular areas are called **groups**. No two groups are adjacent, meaning farmland in one group is **not** four-directionally adjacent to another farmland in a different group.

`land` can be represented by a coordinate system where the top left corner of `land` is `(0, 0)` and the bottom right corner of `land` is `(m-1, n-1)`. Find the coordinates of the top left and bottom right corner of each **group** of farmland. A **group** of farmland with a top left corner at `(r1, c1)` and a bottom right corner at `(r2, c2)` is represented by the 4-length array `[r1, c1, r2, c2].`

Return _a 2D array containing the 4-length arrays described above for each **group** of farmland in_ `land`_. If there are no groups of farmland, return an empty array. You may return the answer in **any order**_.

**Example 1:**

![](https://assets.leetcode.com/uploads/2021/07/27/screenshot-2021-07-27-at-12-23-15-copy-of-diagram-drawio-diagrams-net.png)

```
**Input:** land = [[1,0,0],[0,1,1],[0,1,1]]
**Output:** [[0,0,0,0],[1,1,2,2]]
**Explanation:**
The first group has a top left corner at land[0][0] and a bottom right corner at land[0][0].
The second group has a top left corner at land[1][1] and a bottom right corner at land[2][2].
```

**Example 2:**

![](https://assets.leetcode.com/uploads/2021/07/27/screenshot-2021-07-27-at-12-30-26-copy-of-diagram-drawio-diagrams-net.png)

```
**Input:** land = [[1,1],[1,1]]
**Output:** [[0,0,1,1]]
**Explanation:**
The first group has a top left corner at land[0][0] and a bottom right corner at land[1][1].
```

**Example 3:**

![](https://assets.leetcode.com/uploads/2021/07/27/screenshot-2021-07-27-at-12-32-24-copy-of-diagram-drawio-diagrams-net.png)

```
**Input:** land = [[0]]
**Output:** []
**Explanation:**
There are no groups of farmland.
```

**Constraints:**

* `m == land.length`
* `n == land[i].length`
* `1 <= m, n <= 300`
* `land` consists of only `0`'s and `1`'s.
* Groups of farmland are **rectangular** in shape.

## ac

```java
```
