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import java.util.*;
public class Ch2 {
public static void main(String[] args) {
List<Integer> list1 = new ArrayList<>(List.of(1,1,2,2,2,3));
List<Integer> list2 = new ArrayList<>(List.of(2,3,1,3,2));
List<Integer> list3 = new ArrayList<>(List.of(-1,1,-6,4,5,-6,1,4,1));
frequency_sort(list1);
frequency_sort(list2);
frequency_sort(list3);
System.out.println(list1);
System.out.println(list2);
System.out.println(list3);
}
private static void frequency_sort(List<Integer> list){
HashMap<Integer,Integer> hashMap = new HashMap<>();
for(Integer i : list){
int c = hashMap.getOrDefault(i,0);
hashMap.put(i,c+1);
}
list.sort(new Comparator<>() {
@Override
public int compare(Integer t1, Integer t2) {
int a = hashMap.get(t1);
int b = hashMap.get(t2);
return Objects.equals(a,b) ? Integer.compare(t2,t1)
: Integer.compare(a,b);
}
});
}
}
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