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Java-based LeetCode algorithm problem solutions, regularly updated

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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.`