Q4 PepCoding | Count Distinct Elements In Every Window Of Size K

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Mon Jan 23 2023 07:57:31 GMT+0000 (Coordinated Universal Time)

Saved by @Ayush_dabas07 

import java.util.*;

public class Main {

	public static ArrayList<Integer> solution(int[] arr, int k) {
		ArrayList<Integer> res = new ArrayList<>();
        
        HashMap<Integer,Integer> map = new HashMap<>();
        
        int j = 0 ;
        
        //adding first k elements in the hashmap
        while(j<k){
            
            int of = map.getOrDefault(arr[j],0);
            
            map.put(arr[j],of+1);
            j++;
        }
        res.add(map.size());
        
//moving the window of K at one unit        
        for(int i =0 ; j < arr.length ; j++,i++){
            
            int last = arr[i];
            //removing last element frequency of the window
            int of = map.get(arr[i]);
            of--;
            
            if(of == 0){
                map.remove(last);
            }
            else{
                map.put(last , of);
            }
            
            //adding next element of the window
            map.put(arr[j] , map.getOrDefault(arr[j],0)+1);
            
            res.add(map.size());
            
        }
		
		return res;
	}
	
	public static void main(String[] args) {
		Scanner scn = new Scanner(System.in);
		int[] arr = new int[scn.nextInt()];
		for (int i = 0; i < arr.length; i++) {
			arr[i] = scn.nextInt();
		}
		int k = scn.nextInt();
		ArrayList<Integer> ans = solution(arr,k);
		for(int a : ans){
			System.out.print(a + " ");
		}
	}


}
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https://www.pepcoding.com/resources/data-structures-and-algorithms-in-java-levelup/hashmap-and-heaps/count-distinct-elements-in-every-window-of-size-k-official/ojquestion