There is a garden with N slots. In each slot, there is a flower. The N flowers will bloom one by one in N days. In each day, there will be exactly one flower blooming and it will be in the status of blooming since then.
Given an array flowers consists of number from 1 to N. Each number in the array represents the place where the flower will open in that day.
For example, flowers[i] = x means that the unique flower that blooms at day i will be at position x, where i and x will be in the range from 1 to N.
Also given an integer k, you need to output in which day there exists two flowers in the status of blooming, and also the number of flowers between them is k and these flowers are not blooming.
If there isn’t such day, output -1.
Explanation: In the second day, the first and the third flower have become blooming.
The given array will be in the range [1, 20000].
这道题是我上周才做过的Google内推OA题（这次Contest的另一道题681. Next Closest Time则是第一题，这是第二题，LC真是消息灵通啊）。不过有一点小不一样，就是Google的OA没有要求靠近两边的连续未开花花圃不算数。