import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

public class Practice {
    public static Map<Character, List<String>> groupByFirstLetter(List<String> words) {
        // TODO: map each first letter to a list of words, preserving encounter order.
        return new LinkedHashMap<>();
    }

    public static Map<Integer, List<String>> groupByLength(List<String> words) {
        // TODO: map each word length to a list of words, preserving encounter order.
        return new LinkedHashMap<>();
    }
}