ArrayList<Integer> list = new ArrayList<Integer>();
        for(int i=0;i<arr.length;i++){
            HashSet s = new HashSet();
             int count=0;
             int j=i;
            
          while(count<k && arr.length-i>=k){
              int brr[] = new int[k];
               
              brr[count] =arr[j];
              s.add(brr[count]);
               
              count++;
              j++;
          }
          // System.out.println(s.toString());
          if(s.size()!=0)
          list.add(s.size());
        }
        return list  
==================================================================================
O(n^2)
O(n)
===================================================================================
first we will take k elements in that I will find distinct count
here my sliding window length is k
I will take one more loop 
Each time i will extend window for one more element , i will remove one element at the beginning
//al=2
k=3
1, 2,2,3,3,4,5,6,7,7, 8
====================================================
class Solution {
    public int longestkSubstr(String s, int k) {
        // code here
        int release=0;
        HashMap<Character,Integer> hm=new HashMap<>();
        int maxlen=-1;
        int x=0;
        for(int i=0;i<s.length();i++){
            
             if(hm.containsKey(s.charAt(i))){
                 x=hm.get(s.charAt(i));
                x++;
                hm.put(s.charAt(i),x);
            }else{
                hm.put(s.charAt(i),1);
            }
            
            while(hm.size()>k){
                 x=hm.get(s.charAt(release));
                x--;
                hm.put(s.charAt(release),x);
                if(hm.get(s.charAt(release))==0){
                    hm.remove(s.charAt(release));
                }
                release++;
            }
            
            if(hm.size()==k){
                maxlen=Math.max(maxlen,i-release+1);
            }
            
        }
        return maxlen;
    }
}
==========================================================

2 Sum equal to k
===========================================================