You are given a?0-indexed?permutation of?n?integers?nums.

A permutation is called?semi-ordered?if the first number equals?1?and the last number equals?n. You can perform the below operation as many times as you want until you make?nums?a?semi-ordered?permutation:

• Pick two adjacent elements in?nums, then swap them.

Return?the minimum number of operations to make?nums?a?semi-ordered permutation.

A?permutation?is a sequence of integers from?1?to?n?of length?n?containing each number exactly once.

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Example 1:

Input: nums = [2,1,4,3]Output: 2

Explanation: We can make the permutation semi-ordered using these sequence of operations: 1 - swap i = 0 and j = 1. The permutation becomes [1,2,4,3]. 2 - swap i = 2 and j = 3. The permutation becomes [1,2,3,4]. It can be proved that there is no sequence of less than two operations that make nums a semi-ordered permutation.

Example 2:

Input: nums = [2,4,1,3]Output: 3

Explanation: We can make the permutation semi-ordered using these sequence of operations: 1 - swap i = 1 and j = 2. The permutation becomes [2,1,4,3]. 2 - swap i = 0 and j = 1. The permutation becomes [1,2,4,3]. 3 - swap i = 2 and j = 3. The permutation becomes [1,2,3,4]. It can be proved that there is no sequence of less than three operations that make nums a semi-ordered permutation.

Example 3:

Input: nums = [1,3,4,2,5]Output: 0Explanation: The permutation is already a semi-ordered permutation.

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Constraints:

• 2 <= nums.length == n <= 50

• 1 <= nums[i]?<= 50

• nums is a permutation.

因為是必須2個相鄰的進行翻轉(zhuǎn)，那么我們就找到最大值跟最小值的位置，如果最大值在最小值的左邊，那么他倆一定會進行交換的，所以這時候總的交換次數(shù)減1即可；

其他見代碼：

Runtime:?2 ms, faster than?100.00%?of?Java?online submissions for?Semi-Ordered Permutation.

Memory Usage:?43.5 MB, less than?20.00%?of?Java?online submissions for?Semi-Ordered Permutation.