Given an array A that is a permutation of n numbers [1-n]. Find the number of subarrarys S that meets the following condition max(S) — min(S) = length(S) — 1.

Example 1:

Input: [4, 3, 1, 2, 5] Output: 10 Explanation: subarrays that meets the condition are [4] [3] [1] [2] [5] [4 3] [1 2] [3 1 2] [4 3 1 2] [4 3 1 2 5]

There are 10 subarray that meets the condition, so the answer should be 10.

Is there a better than O(n^2) solution?