## 594. Longest Harmonious Subsequence

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`

## Rust Solution

``````struct Solution;

use std::collections::HashMap;

impl Solution {
fn find_lhs(nums: Vec<i32>) -> i32 {
let mut hs: HashMap<i32, i32> = HashMap::new();
let mut max = 0;
for &x in &nums {
let e = hs.entry(x).or_default();
*e += 1;
}
for (x, u) in &hs {
if let Some(v) = hs.get(&(x - 1)) {
max = i32::max(u + v, max);
}
}
max
}
}

#[test]
fn test() {
let nums = vec![1, 3, 2, 2, 5, 2, 3, 7];
let res = 5;
assert_eq!(Solution::find_lhs(nums), res);
}
``````

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