Kotlin Trie Non-Recursive Delete

trieNonRecursiveDelete.kt

override fun delete(key: String) {
    // search leaf
    key.fold(root) { node, char ->
        node.children[char] ?: return
    }.let { leaf ->
        leaf.value = null
        key.foldRight(leaf) { char, current ->
            if (current.children.isEmpty() && current.value == null) {
                current.parent?.apply { children.remove(char) } ?: return
            } else return
        }
    }
}