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

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