LeetCode 2717. Semi-Ordered Permutation
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.
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.
Constraints:
2 <= nums.length == n <= 501 <= nums[i] <= 50nums is a permutation.
因为是必须2个相邻的进行翻转，那么我们就找到最大值跟最小值的位置，如果最大值在最小值的左边，那么他俩一定会进行交换的，所以这时候总的交换次数减1即可；
其他见代码：
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.
