683. K Empty Slots

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 everyday 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 , find out 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

 

Note:

1. 1 <= N <= 20000
2. 1 <= bulbs[i] <= N
3. bulbs  is a permutation of numbers from  1  to  N .
4. 0 <= K <= 20000