java - 对单词字符进行排序的问题

Question

我有一个问题，我已经困扰了一段时间了。给定一个由英文字母的小写字母或大写字母组成的单词，对这些字符进行排序，以便在该单词中最常出现的字符出现在第一个位置，如果它们出现的次数相同，那么它们将按字典顺序排序。如:

input: Instructions

output: iinnssttcoru

到目前为止我已经写了这篇文章，但从这里我不知道如何对它们进行排序并正确显示，有什么提示吗？

public class Main {
public static void main(String[] args) throws IOException {
    String testString = " ";
    BufferedReader rd = new BufferedReader(new InputStreamReader(System.in));
    testString = rd.readLine();
    Map<Character, List<Character>> map = new HashMap<>();
    for (int i = 0; i < testString.length(); i++) {
        char someChar = testString.charAt(i);
        if (someChar == ' ') {
            continue;
        }
        char ch = testString.charAt(i);
        List<Character> characters = map.getOrDefault(Character.toLowerCase(ch), new ArrayList<>());
        characters.add(ch);
        map.put(Character.toLowerCase(ch), characters);
    }
    List<Map.Entry<Character, List<Character>>> list = new ArrayList<>(map.entrySet());}

Answer 1

您可以添加TreeMap counterAppear，其中key是字符的重复次数，value是具有相同字符的列表key 重复次数。该 list 在打印前需要进行排序，以确保顺序符合要求。使用 TreeMap 确保 map 按键(重复次数)排序。

public static void main(String[] args) throws IOException {
        String testString = " ";
        BufferedReader rd = new BufferedReader(new InputStreamReader(System.in));
        testString = rd.readLine();
        Map<Character, List<Character>> map = new HashMap<>();
        for (int i = 0; i < testString.length(); i++) {
            char someChar = testString.charAt(i);
            if (someChar == ' ') {
                continue;
            }
            char ch = testString.charAt(i);
            //Change to Optimize Code
            Character keyCharacter = Character.toLowerCase(ch);
            if (map.get(keyCharacter) == null) {
                map.put(keyCharacter, new ArrayList<>());
            }
            List<Character> characters = map.get(keyCharacter);
            characters.add(ch);
        }
        TreeMap<Integer, List<Character>> counterAppear = new TreeMap<>();
        for (Map.Entry<Character, List<Character>> entry : map.entrySet()) {
            Character character = entry.getKey();
            int repeatCharTime = entry.getValue().size();
            if (counterAppear.get(repeatCharTime) == null) {
                counterAppear.put(repeatCharTime, new ArrayList<>());
            }
            List<Character> characters = counterAppear.get(repeatCharTime);
            characters.add(character);
        }

        for (Integer repeatCharTime : counterAppear.descendingKeySet()) {
            List<Character> keyCharacters = counterAppear.get(repeatCharTime);
            Collections.sort(keyCharacters);
            for (Character character : keyCharacters) {
                for (int i = 0; i < repeatCharTime; i++) {
                    System.err.print(character);
                }
            }
        }
    }