Second.java

import java.util.*;
    public class test {
        public static void main(String[] args) {
            Scanner in = new Scanner(System.in);
            Deque deque = new ArrayDeque<>();
            Map map = new HashMap();
            int n = in.nextInt();
            int m = in.nextInt();
            int uniqueIntegerArray = 0;
            int answer = 0;

            for (int i = 0; i < n; i++) {
                int num = in.nextInt();
                deque.addLast(num);
                try{
                    int temp = (int)map.get(num);
                    map.remove(num);
                    map.put( num , temp + 1 );
                }catch(Exception e){
                    uniqueIntegerArray ++;
                    map.put(num, 1);
                }
                
                
                
                // subsequence is full
                if( i >= m ){
                    int first = (int)deque.pollFirst();
                    // map에 여러개 있으면
                    int mapCount = (int)map.get(first);
                    if( mapCount > 1 ){
                        map.put( first , mapCount - 1);
                    }
                    // map에 한 개 밖에 없었으면
                    else{
                        map.remove(first);
                        uniqueIntegerArray--;
                    }
                }
                if( answer < uniqueIntegerArray )
                    answer = uniqueIntegerArray;
            }
            System.out.println(answer);
        }
    }