# 1826. Faulty Sensor

<https://leetcode.com/problems/faulty-sensor>

## Description

An experiment is being conducted in a lab. To ensure accuracy, there are **two** sensors collecting data simultaneously. You are given two arrays `sensor1` and `sensor2`, where `sensor1[i]` and `sensor2[i]` are the `ith` data points collected by the two sensors.

However, this type of sensor has a chance of being defective, which causes **exactly one** data point to be dropped. After the data is dropped, all the data points to the **right** of the dropped data are **shifted** one place to the left, and the last data point is replaced with some **random value**. It is guaranteed that this random value will **not** be equal to the dropped value.

* For example, if the correct data is `[1,2,**3**,4,5]` and `3` is dropped, the sensor could return `[1,2,4,5,**7**]` (the last position can be **any** value, not just `7`).

We know that there is a defect in **at most one** of the sensors. Return *the sensor number (*`1` *or* `2`*) with the defect. If there is **no defect** in either sensor or if it is **impossible** to determine the defective sensor, return* `-1`*.*

**Example 1:**

```
**Input:** sensor1 = [2,3,4,5], sensor2 = [2,1,3,4]
**Output:** 1
**Explanation:** Sensor 2 has the correct values.
The second data point from sensor 2 is dropped, and the last value of sensor 1 is replaced by a 5.
```

**Example 2:**

```
**Input:** sensor1 = [2,2,2,2,2], sensor2 = [2,2,2,2,5]
**Output:** -1
**Explanation:** It is impossible to determine which sensor has a defect.
Dropping the last value for either sensor could produce the output for the other sensor.
```

**Example 3:**

```
**Input:** sensor1 = [2,3,2,2,3,2], sensor2 = [2,3,2,3,2,7]
**Output:** 2
**Explanation:** Sensor 1 has the correct values.
The fourth data point from sensor 1 is dropped, and the last value of sensor 1 is replaced by a 7.
```

**Constraints:**

* `sensor1.length == sensor2.length`
* `1 <= sensor1.length <= 100`
* `1 <= sensor1[i], sensor2[i] <= 100`

## ac

```java
```
