Решение

class Solution {
    fun detectCapitalUse(word: String): Boolean {
        val n = word.length
        if (n <= 1) return true
        val firstUpper = isUpper(word[0])
        val secondUpper = isUpper(word[1])
        if (!firstUpper && secondUpper) return false
        val expectUpper = firstUpper && secondUpper
        for (i in 2 until n) {
            if (isUpper(word[i]) != expectUpper) return false
        }
        return true
    }

    private fun isUpper(c: Char): Boolean {
        return c >= 'A' && c <= 'Z'
    }
}