Longest Consecutive Sequence

 public int longestConsecutive(int[] num) {
        if(num==null|| num.length==0) return 0;
        int  res = 1;
        HashSet<Integer> hs = new HashSet<Integer>();
        for(int i=0; i<num.length; i++){
            hs.add(num[i]);
        }
         
        while(!hs.isEmpty()){
            Iterator it  = hs.iterator();
            int item = (Integer) it.next();
            //dont forget this
            hs.remove(item);
            int cnt = 1;
            int less = item-1;
            int more = item+1;
            while(hs.contains(less)){
                cnt++;
                hs.remove(less--);
            }
            while(hs.contains(more)){
                cnt++;
                hs.remove(more++);
            }
            res = Math.max(res,cnt);
        }
        return res;
    }