Note that there are two different meanings of “ordered” in this context. In an ordered hash map (like PHP, JavaScript, and Python) it means insertion order. But

Note that there are two different meanings of “ordered” in this context. In an ordered hash map (like PHP, JavaScript, and Python) it means insertion order. But the article is talking about lexicographic order, for which you need a tree structure of some kind (binary tree, btree, trie, or this article’s fst).