fun noPrefix(words: Array<String>): Unit {
    // Write your code here
    val tree = Node("")
    for (word in words) {
        var key = tree.text
        var parentNode = tree
        for (char in word) {
            key += char
            val node = parentNode.children.find { it.text == key } ?: Node(key)
                .also(parentNode.children::add)
            if (node.isWord) {
                println("BAD SET")
                println(word)
                return
            }
            parentNode = node
        }
        if (parentNode.children.isNotEmpty()) {
            println("BAD SET")
            println(word)
            return
        }
        parentNode.isWord = true
    }
    println("GOOD SET")
}

data class Node(
    var text: String,
    var isWord: Boolean = false,
    var children: MutableCollection<Node> = mutableListOf(),
) {
}