# 0587. Erect the Fence

<https://leetcode.com/problems/erect-the-fence>

## Description

You are given an array `trees` where `trees[i] = [xi, yi]` represents the location of a tree in the garden.

You are asked to fence the entire garden using the minimum length of rope as it is expensive. The garden is well fenced only if **all the trees are enclosed**.

Return *the coordinates of trees that are exactly located on the fence perimeter*.

**Example 1:**

![](https://assets.leetcode.com/uploads/2021/04/24/erect2-plane.jpg)

```
**Input:** points = [[1,1],[2,2],[2,0],[2,4],[3,3],[4,2]]
**Output:** [[1,1],[2,0],[3,3],[2,4],[4,2]]
```

**Example 2:**

![](https://assets.leetcode.com/uploads/2021/04/24/erect1-plane.jpg)

```
**Input:** points = [[1,2],[2,2],[4,2]]
**Output:** [[4,2],[2,2],[1,2]]
```

**Constraints:**

* `1 <= points.length <= 3000`
* `points[i].length == 2`
* `0 <= xi, yi <= 100`
* All the given points are **unique**.

## ac

```java
```