1차 풀이

import java.util.Comparator;
import java.util.PriorityQueue;

class Solution {
    public int solution(int scoreMax, int appleNum, int[] scores) {
        int answer = 0;
        PriorityQueue<Integer> pq = new PriorityQueue<>(Comparator.reverseOrder());
        for (int j : scores) {
            pq.offer(j);
        }

        while (pq.size() >= appleNum) {
            int min = Integer.MAX_VALUE;
            for (int i = 0; i < appleNum; i++) {
                int appleScore = pq.poll();
                min = Math.min(min, appleScore);
            }
            answer += (min * appleNum);
        }

        return answer;
    }
}

2차 풀이

import java.util.Comparator;
import java.util.PriorityQueue;

class Solution {
    public int solution(int scoreMax, int appleNum, int[] scores) {
        int answer = 0;
        PriorityQueue<Integer> pq = new PriorityQueue<>(Comparator.reverseOrder());
        for (int j : scores) {
            pq.offer(j);
        }

        while (pq.size() >= appleNum) {
            int min = Integer.MAX_VALUE;
            for (int i = 0; i < appleNum; i++) {
                min = pq.poll();
            }
            answer += (min * appleNum);
        }

        return answer;
    }
}

3차 풀이 (정답 참고)

import java.util.Arrays;

class Solution {
    public int solution(int scoreMax, int appleNum, int[] scores) {
        int answer = 0;

        Arrays.sort(scores);

        int idx = scores.length;

        while (idx >= appleNum) {
            answer += (scores[idx - appleNum] * appleNum);

            idx -= appleNum;
        }

        return answer;
    }
}