/*
    genres, plays
    
    classic -> 500 + 150 + 800 = 1450
    pop -> 600 + 2500 = 3100
*/
 
function solution(genres, plays) {
    // TODO: 장르 합 대소 구분, 장르별 횟수 구분
    let genreHash = new Map();
    let playHash = new Map();
    
    for (let i = 0; i < genres.length; i += 1) {
        genreHash.set(genres[i], (genreHash.get(genres[i]) || 0) + plays[i]);
        
        if (!playHash.has(genres[i])) playHash.set(genres[i], []);
        playHash.get(genres[i]).push({ id: i, count: plays[i] });
    }
    
    const sortedGenreHash = [...genreHash.entries()].sort((a, b) => b[1] - a[1]);
    
    const result = [];
 
    sortedGenreHash.forEach(([genre, total]) => {
        const topTwosongs = playHash.get(genre)
            .sort((a, b) => b.count - a.count)
            .slice(0, 2);
 
        topTwosongs.forEach(s => result.push(s.id));
    });
 
    return result;
}