# 0683. K Empty Slots

https://leetcode.com/problems/k-empty-slots

## Description

You have `n` bulbs in a row numbered from `1` to `n`. Initially, all the bulbs are turned off. We turn on **exactly one** bulb every day until all bulbs are on after `n` days.

You are given an array `bulbs` of length `n` where `bulbs[i] = x` means that on the `(i+1)th` day, we will turn on the bulb at position `x` where `i` is **0-indexed** and `x` is **1-indexed.**

Given an integer `k`, return _the **minimum day number** such that there exists two **turned on** bulbs that have **exactly**_ _`k` bulbs between them that are **all turned off**. If there isn't such day, return `-1`._

**Example 1:**

```
**Input:** bulbs = [1,3,2], k = 1
**Output:** 2
**Explanation:**
On the first day: bulbs[0] = 1, first bulb is turned on: [1,0,0]
On the second day: bulbs[1] = 3, third bulb is turned on: [1,0,1]
On the third day: bulbs[2] = 2, second bulb is turned on: [1,1,1]
We return 2 because on the second day, there were two on bulbs with one off bulb between them.
```

**Example 2:**

```
**Input:** bulbs = [1,2,3], k = 1
**Output:** -1
```

**Constraints:**

* `n == bulbs.length`
* `1 <= n <= 2 * 104`
* `1 <= bulbs[i] <= n`
* `bulbs` is a permutation of numbers from `1` to `n`.
* `0 <= k <= 2 * 104`

## ac

```java
```
