[Kotlin] Two-liner Using partition and intersect
\nclass Solution {\n    fun greatestLetter(s: String): String {\n        val (lower, upper) = s.asSequence().partition { it.isLowerCase() }\n        return lowe
```\nclass Solution {\n    fun greatestLetter(s: String): String {\n        val (lower, upper) = s.asSequence().partition { it.isLowerCase() }\n        return lower.map { it.toUpperCase() }.intersect(upper).max()?.toString() ?: ""\n    }\n}\n```
['Kotlin']