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# 2015. Average Height of Buildings in Each Segment

<https://leetcode.com/problems/average-height-of-buildings-in-each-segment>

## Description

A perfectly straight street is represented by a number line. The street has building(s) on it and is represented by a 2D integer array `buildings`, where `buildings[i] = [starti, endi, heighti]`. This means that there is a building with `heighti` in the **half-closed segment** `[starti, endi)`.

You want to **describe** the heights of the buildings on the street with the **minimum** number of non-overlapping **segments**. The street can be represented by the 2D integer array `street` where `street[j] = [leftj, rightj, averagej]` describes a **half-closed segment** `[leftj, rightj)` of the road where the **average** heights of the buildings in the **segment** is `averagej`.

* For example, if `buildings = [[1,5,2],[3,10,4]],` the street could be represented by `street = [[1,3,2],[3,5,3],[5,10,4]]` because:
  * From 1 to 3, there is only the first building with an average height of `2 / 1 = 2`.
  * From 3 to 5, both the first and the second building are there with an average height of `(2+4) / 2 = 3`.
  * From 5 to 10, there is only the second building with an average height of `4 / 1 = 4`.

Given `buildings`, return *the 2D integer array* `street` *as described above (**excluding** any areas of the street where there are no buldings). You may return the array in **any order***.

The **average** of `n` elements is the **sum** of the `n` elements divided (**integer division**) by `n`.

A **half-closed segment** `[a, b)` is the section of the number line between points `a` and `b` **including** point `a` and **not including** point `b`.

**Example 1:**

![](https://assets.leetcode.com/uploads/2021/09/21/image-20210921224001-2.png)

```
**Input:** buildings = [[1,5,2],[3,10,4]]
**Output:** [[1,3,2],[3,5,3],[5,10,4]]
**Explanation:**
From 1 to 3, there is only the first building with an average height of 2 / 1 = 2.
From 3 to 5, both the first and the second building are there with an average height of (2+4) / 2 = 3.
From 5 to 10, there is only the second building with an average height of 4 / 1 = 4.
```

**Example 2:**

```
**Input:** buildings = [[1,3,2],[2,5,3],[2,8,3]]
**Output:** [[1,3,2],[3,8,3]]
**Explanation:**
From 1 to 2, there is only the first building with an average height of 2 / 1 = 2.
From 2 to 3, all three buildings are there with an average height of (2+3+3) / 3 = 2.
From 3 to 5, both the second and the third building are there with an average height of (3+3) / 2 = 3.
From 5 to 8, there is only the last building with an average height of 3 / 1 = 3.
The average height from 1 to 3 is the same so we can group them into one segment.
The average height from 3 to 8 is the same so we can group them into one segment.
```

**Example 3:**

```
**Input:** buildings = [[1,2,1],[5,6,1]]
**Output:** [[1,2,1],[5,6,1]]
**Explanation:**
From 1 to 2, there is only the first building with an average height of 1 / 1 = 1.
From 2 to 5, there are no buildings, so it is not included in the output.
From 5 to 6, there is only the second building with an average height of 1 / 1 = 1.
We cannot group the segments together because an empty space with no buildings seperates the segments.
```

**Constraints:**

* `1 <= buildings.length <= 105`
* `buildings[i].length == 3`
* `0 <= starti < endi <= 108`
* `1 <= heighti <= 105`

## ac

```java
```