static class TrieNode{

        HashMap<Character, TrieNode> child;
        List<String> list;
        boolean isWord;

        public TrieNode(){
            child = new HashMap<>();
            list = new ArrayList<>();
        }
    }
    public static List<List<String>> searchSuggestions(List<String> repository, String customerQuery) {
    List<List<String>> res = new ArrayList<>();
    Collections.sort(repository);
    TrieNode root = buildTree(repository);
    TrieNode curr = root;
    boolean flag = false;
    for (int i=0; i<customerQuery.length(); i++){
        char key = customerQuery.charAt(i);
        curr = curr.child.get(key);
        if (curr == null){
            flag = true;
            break;
        }
        if (i > 0){
            List<String> temp = new ArrayList<>();
			List<String> words = curr.list;
			for (int j=0; j<3 && j < words.size(); j++)
				temp.add(words.get(j).toLowerCase());
            res.add(temp);
        }
    }
    return res;
    }

    public static TrieNode buildTree(List<String> repository){
        TrieNode root = new TrieNode();
        for (String s : repository){
            TrieNode curr = root;
            for (int i=0; i<s.length(); i++){
                char key = s.charAt(i);
                if (curr.child.get(key) == null){
                    curr.child.put(key, new TrieNode());
                }
                curr = curr.child.get(key);
                curr.list.add(s);
            }
            curr.isWord = true;
        }
        return root;
    }