Leetcode 451. Sort Characters By Frequency

451. Sort Characters By Frequency

難易度

Medium

アプローチ

Hashmap

class Solution {
    public String frequencySort(String s) {
        HashMap<Character, Integer> hashMap = new HashMap<>();

        for (char c : s.toCharArray()) {
            hashMap.put(c, hashMap.getOrDefault(c, 0) + 1);
        }

        return hashMap.entrySet().stream()
                .sorted(Map.Entry.comparingByValue((o1, o2) -> -o1.compareTo(o2)))
                .map(entry -> String.valueOf(entry.getKey()).repeat(entry.getValue()))
                .map(String::valueOf)
                .collect(Collectors.joining());

/*
        return hashMap.entrySet().stream()
                .sorted((o1, o2) -> o2.getValue() - o1.getValue())
                .map(obj -> String.valueOf(obj.getKey()).repeat(obj.getValue()))
                .map(String::valueOf)
                .collect(Collectors.joining());
*/
    }
}

• こちらの回答を参照しました