add PROGRAMMERS-42579

Author: codejsha

README.md

@@ -28,6 +28,7 @@
 | PROGRAMMERS-17687         | [java](programmers/problem17687)   | [n진수 게임 (n-base Game)](https://school.programmers.co.kr/learn/courses/30/lessons/17687)                                           |
 | PROGRAMMERS-42577         | [java](programmers/problem42577)   | [전화번호 목록 (List of Phone Numbers)](https://school.programmers.co.kr/learn/courses/30/lessons/42577)                              |
 | PROGRAMMERS-42578         | [python](programmers/problem42578) | [의상 (Clothes)](https://school.programmers.co.kr/learn/courses/30/lessons/42578)                                                     |
+| PROGRAMMERS-42579         | [java](programmers/problem42579)   | [베스트앨범 (Best Album)](https://school.programmers.co.kr/learn/courses/30/lessons/42579)                                             |
 | PROGRAMMERS-42586         | [java](programmers/problem42586)   | [기능개발 (Function Development)](https://school.programmers.co.kr/learn/courses/30/lessons/42586)                                    |
 | PROGRAMMERS-42587         | [java](programmers/problem42587)   | [프로세스 (Process)](https://school.programmers.co.kr/learn/courses/30/lessons/42587)                                                 |
 | PROGRAMMERS-42626         | [java](programmers/problem42626)   | [더 맵게 (Spicier)](https://school.programmers.co.kr/learn/courses/30/lessons/42626)                                                  |

programmers/problem42579/BestAlbum.java

@@ -0,0 +1,48 @@
+package problem42579;
+
+import java.util.*;
+
+public class BestAlbum {
+    public static void main(String[] args) {
+        var sol = new BestAlbum();
+        var genres1 = new String[]{"classic", "pop", "classic", "classic", "pop"};
+        var plays1 = new int[]{500, 600, 150, 800, 2500};
+        var expected1 = new int[]{4, 1, 3, 0};
+        var result1 = sol.solution(genres1, plays1);
+        System.out.println("test1: expected: " + Arrays.toString(expected1) + ", result: " + Arrays.toString(result1));
+    }
+
+    public int[] solution(String[] genres, int[] plays) {
+        var genrePlays = new HashMap<String, Integer>();
+        var genreMusic = new HashMap<String, List<HashMap<Integer, Integer>>>();
+        for (int i = 0; i < genres.length; i++) {
+            var genre = genres[i];
+            var play = plays[i];
+            genrePlays.put(genre, genrePlays.getOrDefault(genre, 0) + play);
+
+            var music = new HashMap<Integer, Integer>();
+            music.put(i, play);
+            var list = genreMusic.getOrDefault(genre, new ArrayList<>());
+            list.add(music);
+            genreMusic.put(genre, list);
+        }
+
+        var genreList = new ArrayList<>(List.of(genrePlays.keySet().toArray(String[]::new)));
+        genreList.sort((a, b) -> genrePlays.get(b) - genrePlays.get(a));
+
+        var answer = new ArrayList<Integer>();
+        for (var genre : genreList) {
+            var musicList = genreMusic.get(genre);
+            musicList.sort((a, b) -> b.values().iterator().next() - a.values().iterator().next());
+            var count = 0;
+            for (var music : musicList) {
+                answer.add(music.keySet().iterator().next());
+                count++;
+                if (count == 2) {
+                    break;
+                }
+            }
+        }
+        return answer.stream().mapToInt(i -> i).toArray();
+    }
+}