Решение

class Solution {
    fun findLHS(nums: IntArray): Int {
        val map = HashMap<Int, Int>(nums.size * 2)
        for (x in nums) {
            map[x] = (map[x] ?: 0) + 1
        }
        var ans = 0
        for ((k, v) in map) {
            val v2 = map[k + 1]
            if (v2 != null) {
                val len = v + v2
                if (len > ans) ans = len
            }
        }
        return ans
    }
}