# 1964. Find the Longest Valid Obstacle Course at Each Position

<https://leetcode.com/problems/find-the-longest-valid-obstacle-course-at-each-position>

## Description

You want to build some obstacle courses. You are given a **0-indexed** integer array `obstacles` of length `n`, where `obstacles[i]` describes the height of the `ith` obstacle.

For every index `i` between `0` and `n - 1` (**inclusive**), find the length of the **longest obstacle course** in `obstacles` such that:

* You choose any number of obstacles between `0` and `i` **inclusive**.
* You must include the `ith` obstacle in the course.
* You must put the chosen obstacles in the **same order** as they appear in `obstacles`.
* Every obstacle (except the first) is **taller** than or the **same height** as the obstacle immediately before it.

Return *an array* `ans` *of length* `n`, *where* `ans[i]` *is the length of the **longest obstacle course** for index* `i` *as described above*.

**Example 1:**

```
**Input:** obstacles = [1,2,3,2]
**Output:** [1,2,3,3]
**Explanation:** The longest valid obstacle course at each position is:
- i = 0: [1], [1] has length 1.
- i = 1: [1,2], [1,2] has length 2.
- i = 2: [1,2,3], [1,2,3] has length 3.
- i = 3: [1,2,3,2], [1,2,2] has length 3.
```

**Example 2:**

```
**Input:** obstacles = [2,2,1]
**Output:** [1,2,1]
**Explanation:** The longest valid obstacle course at each position is:
- i = 0: [2], [2] has length 1.
- i = 1: [2,2], [2,2] has length 2.
- i = 2: [2,2,1], [1] has length 1.
```

**Example 3:**

```
**Input:** obstacles = [3,1,5,6,4,2]
**Output:** [1,1,2,3,2,2]
**Explanation:** The longest valid obstacle course at each position is:
- i = 0: [3], [3] has length 1.
- i = 1: [3,1], [1] has length 1.
- i = 2: [3,1,5], [3,5] has length 2. [1,5] is also valid.
- i = 3: [3,1,5,6], [3,5,6] has length 3. [1,5,6] is also valid.
- i = 4: [3,1,5,6,4], [3,4] has length 2. [1,4] is also valid.
- i = 5: [3,1,5,6,4,2], [1,2] has length 2.
```

**Constraints:**

* `n == obstacles.length`
* `1 <= n <= 105`
* `1 <= obstacles[i] <= 107`

## ac

```java
```