BOJ2910 빈도 정렬

https://www.acmicpc.net/problem/2910

2910번: 빈도 정렬

 

링크드해쉬맵을 이용하면 클래스를 만들 필요가 없다.

import java.io.*;
import java.util.*;
public class Main
{
    public static class Num{
        Integer num;
        Integer count;
        Integer idx;
        public Num(Integer num, Integer count, Integer idx){
            this.num=num;
            this.count=count;
            this.idx = idx;
        }
    }
    
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
		
		HashMap<Integer,Integer> hashmap = new HashMap();
		HashMap<Integer,Integer> order = new HashMap();
        String[] input1 = br.readLine().split(" ");
        String[] input2 = br.readLine().split(" ");
        
        int index=0;
        for(String s: input2){
            hashmap.put(Integer.valueOf(s),hashmap.getOrDefault(Integer.valueOf(s),0)+1);
            if(!order.containsKey(Integer.valueOf(s))) {
                order.put(Integer.valueOf(s),index++);            
            }
        }
        
        List<Num> nums = new ArrayList<>();
        
        for(int i=0; i<input2.length; i++){
            nums.add(new Num(Integer.valueOf(input2[i]),hashmap.get(Integer.valueOf(input2[i])),order.get(Integer.valueOf(input2[i]))));
        }
        
        
        
        Collections.sort(nums,(n1,n2)->{
            if(n2.count==n1.count){
                
                return n1.idx-n2.idx;
            }
            return n2.count-n1.count;
        });
		
		for(Num n : nums){
		    bw.write(n.num+" ");
		}
		
		bw.flush();
	}
}

 

 

import java.util.*;

class Main
{
    public static void main (String[] args) {
        Scanner sc = new Scanner(System.in);

        int N = sc.nextInt();
        int C = sc.nextInt();
        Map<Integer, Integer> messages = new LinkedHashMap<>();
        for (int i = 0; i < N; i++) {
            int message = sc.nextInt();
            messages.put(message, messages.getOrDefault(message, 0) + 1);
        }

        Integer[] frequencies = messages.keySet().toArray(new Integer[messages.size()]);
        Arrays.sort(frequencies, new Comparator<Integer>() {
            @Override
            public int compare(Integer o1, Integer o2) {
                return messages.get(o2) - messages.get(o1);
            }
        });

        for (int frequency : frequencies) {
            int count = messages.get(frequency);
            while (count-- > 0)
                System.out.print(frequency + " ");
        }
        System.out.println();
    }
}