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# 0594. Longest Harmonious Subsequence

<https://leetcode.com/problems/longest-harmonious-subsequence>

## Description

We define a harmonious array as an array where the difference between its maximum value and its minimum value is **exactly** `1`.

Given an integer array `nums`, return *the length of its longest harmonious subsequence among all its possible subsequences*.

A **subsequence** of array is a sequence that can be derived from the array by deleting some or no elements without changing the order of the remaining elements.

**Example 1:**

```

**Input:** nums = [1,3,2,2,5,2,3,7]
**Output:** 5
**Explanation:** The longest harmonious subsequence is [3,2,2,2,3].
```

**Example 2:**

```

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

**Example 3:**

```

**Input:** nums = [1,1,1,1]
**Output:** 0
```

**Constraints:**

* `1 <= nums.length <= 2 * 104`
* `-109 <= nums[i] <= 109`

## ac

```java
```