2717 - Semi-Ordered Permutation.

Easy

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: 0

Explanation: The permutation is already a semi-ordered permutation.

Constraints:

• 2 <= nums.length == n <= 50

• 1 <= nums[i] <= 50

• nums is a permutation.