public static String isValid(String s) 
    {
        Map<Character,Integer> map = new HashMap<>();
        for(Character c : s.toCharArray())
        {           
            map.put(c, map.getOrDefault(c, 0) + 1);
        }
       List<Integer> list  = new ArrayList<>(map.values());
       
       Collections.sort(list);
       int min =list.get(0);
       int max= list.get(list.size() - 1);
       if(min == max)
        {
           return "YES";
        }
        int minCount = 0;
        int maxCount = 0;

        for(int val : list)
        {
            if(min == val)
            {
                minCount++;
            }
            if(max == val)
            {
                maxCount++;
            }
        }
        System.out.println("max:"+max+"\n min:"+min);
        System.out.println("maxCount:"+maxCount+"\n minCount:"+minCount);
        if(max - min > 1 )
        {
            if(minCount != 1)
            {
                return "NO";
            }
        }
        return ((maxCount + minCount == list.size() ) && (maxCount < 2 || minCount <2 )  ? "YES": "NO"  );
    }