프로그래머스 베스트앨범(genres) 정답 코드

난이도 ★★★☆☆

 

문제를 보시려면 여기를 클릭

 

 

 

힌트

Java 자료구조 및 Comparable 을 잘 이용하면 쉽게 구현할 수 있습니다. 해시문제인지 정렬문제인지 헷갈리네요.

 

 

 

이하는 코드입니다.

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
 
public class Solution {
    public int[] solution(String[] genres, int[] plays) {
        Map<String, Integer> indexMap = new HashMap<>();
        List<Genre> genreList = new ArrayList<>();
 
        for (int i = 0; i < genres.length; i++) {
            Genre genre;
            Integer index = indexMap.get(genres[i]);
 
            if (index == null) {
                genre = new Genre();
                genreList.add(genre);
 
                indexMap.put(genres[i], genreList.size() - 1);
            }
            else {
                genre = genreList.get(index);
            }
 
            Song song = new Song();
            song.id = i;
            song.play = plays[i];
 
            genre.songs.add(song);
            genre.sum += plays[i];
        }
 
        Collections.sort(genreList);
 
        int count = 0;
 
        for (Genre genre : genreList) {
            Collections.sort(genre.songs);
 
            if (genre.songs.size() > 1) {
                count += 2;
            } else {
                count += 1;
            }
        }
 
        int[] answer = new int[count];
        int answerIdx = 0;
 
        for (Genre genre : genreList) {
            for (int i = 0; i < genre.songs.size() && i < 2; i++) {
                answer[answerIdx] = genre.songs.get(i).id;
                answerIdx++;
            }
        }
 
        return answer;
    }
 
    private class Genre implements Comparable<Genre> {
        int sum;
        List<Song> songs;
 
        public Genre() {
            sum = 0;
            songs = new ArrayList<>();
        }
 
        @Override
        public int compareTo(Genre that) {
            return Integer.compare(that.sum, this.sum); // order by sum desc
        }
    }
 
    private class Song implements Comparable<Song> {
        int id;
        int play;
 
        @Override
        public int compareTo(Song that) {
            if (this.play == that.play) {
                return Integer.compare(this.id, that.id); // order by id asc
            }
 
            return Integer.compare(that.play, this.play); // order by play desc
        }
    }
}