[프로그래머스 코딩테스트 고득점 Kit] 베스트앨범

https://programmers.co.kr/learn/courses/30/lessons/42579

풀이

    index: 고유 번호
    {
        classic: {
          count: 1450,
          songs: [{ index: 3, play: 800 }, { index: 0, play: 500 }]
        },
        pop: {
          count: 3100,
          songs: [{ index: 4, play: 2500 }, { indx: 1, play:600 }]
        }
    }  
    
    1. 인기 순으로 장르를 정렬 => 
    [pop, classic]
    2. 각 노래들을 플레이 횟수 / 인덱스 번호로 정렬 =>
    eachSongs.map(eachSong.sort((a, b) => b.play - a.play || a.index - b.index))
    3. 인덱스 번호 2개 씩 slice
    => [...popSongs.map({ index }) => index).slice(0,2), ...]

function makeAlbumCollection(genres, plays) {
  const albumCollection = {};

  plays.forEach((play, index) => {
    const album = albumCollection[genres[index]];
    if (album) {
      album.count += play;
      album.songs.push({
        play,
        index,
      });
    } else {
      albumCollection[genres[index]] = {
        count: play,
        songs: [
          {
            play,
            index,
          },
        ],
      };
    }
  });

  return albumCollection;
}

function getPopularGenres(collection) {
  return Object.keys(collection).sort(
    (a, b) => collection[b].count - collection[a].count
  );
}

function sortBestSongs(collection) {
  Object.keys(collection).forEach((genre) => {
    collection[genre].songs = collection[genre].songs.sort(
      (a, b) => b.play - a.play || a.index - b.index
    );
  });
}

function solution(genres, plays) {
  const albumCollection = makeAlbumCollection(genres, plays);
  const popularGenres = getPopularGenres(albumCollection);
  sortBestSongs(albumCollection);

  return popularGenres.reduce(
    (acc, genre) =>
      acc.concat(
        albumCollection[genre].songs.map(({ index }) => index).slice(0, 2)
      ),
    []
  );
}