Kotlin Trie Delete Basic

trieBasicDelete.kt

override fun delete(key: String) {
    delete(key, 0, root)
}

private fun delete(key: String, index: Int, node: Node<Value>): Trie.Node<Value>? {
    if (index == key.length) {
        node.value = null
        if (node.children.isEmpty()) return null
        return node
    }

    val child = node.children[key[index]] ?: return null
    val deleteChild = delete(key, index + 1, child) == null
    if (deleteChild) {
        node.children.remove(key[index])
        if (node.children.isEmpty() && node.value == null) return null
    }

    return node
}