Longest harmonious subsequence

Array Hash Table Sliding Window Sorting Counting

64.4% acceptance

Jan 13, 2026

2822

351

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.

Solution

Rust

Time O(n)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn find_lhs(nums: Vec<i32>) -> i32 {
    use std::collections::HashMap;
    let mut freq: HashMap<i32, i32> = HashMap::new();
    for &x in &nums { *freq.entry(x).or_insert(0) += 1; }
    freq.keys().map(|&k| {
      if let Some(&v) = freq.get(&(k + 1)) { freq[&k] + v } else { 0 }
    }).max().unwrap_or(0)
  }
}