594.js

/** ------------------------------------------------------------------------------
 * 
 * 594. Longest Harmonious Subsequence
 * Topics: Hash Table, Sliding Window
 * https://leetcode.com/problems/longest-harmonious-subsequence/description/?envType=daily-question&envId=2025-06-30
 * 
 ------------------------------------------------------------------------------ */
/**
 * @param {number[]} nums
 * @return {number}
 */
var findLHS = function (nums) {
  let max = 0
  let map = new Map()

  for (let i = 0; i < nums.length; i++) {
    if (map.has(nums[i])) {
      map.set(nums[i], map.get(nums[i]) + 1)
    } else {
      map.set(nums[i], 1)
    }
  }

  for (const [num, count] of map) {
    if (map.has(num + 1)) {
      max = Math.max(max, count + map.get(num + 1))
    }
  }

  return max
}

console.log(findLHS([1, 3, 2, 2, 5, 2, 3, 7]))