SearchSuggestionsSystem.java

class Solution {
    public List<List<String>> suggestedProducts(String[] products, String searchWord) {
        List<List<String>> ans = new ArrayList<>();
        TreeMap<String, Integer> map = new TreeMap<>();
        Arrays.sort(products);

        List<String> productsList = Arrays.asList(products);

        for (int i = 0; i < products.length; i++) {
            map.put(products[i], i);
        }

        String key = "";
        for (char c : searchWord.toCharArray()) {
            key += c;
            String ceiling = map.ceilingKey(key);
            String floor = map.floorKey(key + "{");

            if (ceiling == null || floor == null) break;

            ans.add(productsList.subList(map.get(ceiling), Math.min(map.get(ceiling) + 3, map.get(floor) + 1)));
        }

        while (ans.size() < searchWord.length()) ans.add(new ArrayList<>());
        return ans;
    }
}