第一题 用java写的 import java.util.*; public class Main { @SuppressWarnings("resource") public static void main(String[] args){ Scanner sc = new Scanner(System.in); String string = sc.next(); Map<String,Integer> map = new TreeMap<>(new Comparator<String>() { public int compare(String s1, String s2) { return s2.compareTo(s1); } }); for(char c : string.toCharArray()) { String s = String.valueOf(c); map.put(s,map.getOrDefault(s, 0) + 1); } List<Map.Entry<String, Integer>> list = new ArrayList<>(map.entrySet()); Collections.sort(list,(o1, o2) -> o2.getValue() - o1.getValue()); for(Map.Entry<String, Integer> entry : list) { System.out.print(entry.getKey() + ":" + entry.getValue() + ";"); } } } 如果有a和B的次数都最多会先出a然后B，此情况不知符合题意吗