# 1776. Car Fleet II

https://leetcode.com/problems/car-fleet-ii

## Description

There are `n` cars traveling at different speeds in the same direction along a one-lane road. You are given an array `cars` of length `n`, where `cars[i] = [positioni, speedi]` represents:

* `positioni` is the distance between the `ith` car and the beginning of the road in meters. It is guaranteed that `positioni < positioni+1`.
* `speedi` is the initial speed of the `ith` car in meters per second.

For simplicity, cars can be considered as points moving along the number line. Two cars collide when they occupy the same position. Once a car collides with another car, they unite and form a single car fleet. The cars in the formed fleet will have the same position and the same speed, which is the initial speed of the **slowest** car in the fleet.

Return an array `answer`, where `answer[i]` is the time, in seconds, at which the `ith` car collides with the next car, or `-1` if the car does not collide with the next car. Answers within `10-5` of the actual answers are accepted.

**Example 1:**

```
**Input:** cars = [[1,2],[2,1],[4,3],[7,2]]
**Output:** [1.00000,-1.00000,3.00000,-1.00000]
**Explanation:** After exactly one second, the first car will collide with the second car, and form a car fleet with speed 1 m/s. After exactly 3 seconds, the third car will collide with the fourth car, and form a car fleet with speed 2 m/s.
```

**Example 2:**

```
**Input:** cars = [[3,4],[5,4],[6,3],[9,1]]
**Output:** [2.00000,1.00000,1.50000,-1.00000]
```

**Constraints:**

* `1 <= cars.length <= 105`
* `1 <= positioni, speedi <= 106`
* `positioni < positioni+1`

## ac

```java
```
