以下两种方式都可以 注意核心思想一定是先从小到大培排序 取第一个 和最后2个 组合成一组 取中间数
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int n= scanner.nextInt();
List<integer> resultList = new ArrayList<>();
while (scanner.hasNext()){
resultList.add(scanner.nextInt());
}
Collections.sort(resultList);
long result = 0;
for (int i=0;i< n ;i++){
result +=resultList.get(3n -2(i+1));
}
System.out.println(result);
}</integer>

public static void test1() {
Scanner scanner = new Scanner(System.in);
int n;
long[] data;
while(scanner.hasNext()){
n=scanner.nextInt();
data = new long[3n];
for (int i = 0; i <data.length ; i++) {
data[i] = scanner.nextLong();
}
Arrays.sort(data);
long result = 0;
for (int i = 0; i < n; i++) {
result+=data[data.length-(2(i+1))];
}
System.out.println(result);
}

}