# 0765. Couples Holding Hands

<https://leetcode.com/problems/couples-holding-hands>

## Description

There are `n` couples sitting in `2n` seats arranged in a row and want to hold hands.

The people and seats are represented by an integer array `row` where `row[i]` is the ID of the person sitting in the `ith` seat. The couples are numbered in order, the first couple being `(0, 1)`, the second couple being `(2, 3)`, and so on with the last couple being `(2n - 2, 2n - 1)`.

Return *the minimum number of swaps so that every couple is sitting side by side*. A swap consists of choosing any two people, then they stand up and switch seats.

**Example 1:**

```
**Input:** row = [0,2,1,3]
**Output:** 1
**Explanation:** We only need to swap the second (row[1]) and third (row[2]) person.
```

**Example 2:**

```
**Input:** row = [3,2,0,1]
**Output:** 0
**Explanation:** All couples are already seated side by side.
```

**Constraints:**

* `2n == row.length`
* `2 <= n <= 30`
* `n` is even.
* `0 <= row[i] < 2n`
* All the elements of `row` are **unique**.

## ac

```java
```