longest consecutive sequence

class  {
    public int longestConsecutive(int[] nums) {
        HashMap<Integer,Integer> map=new HashMap<>();
        int res=0;
        for(int n:nums)
        {
            if(!map.containsKey(n))
            {
            int left=map.containsKey(n-1)? map.get(n-1): 0;
            int right=map.containsKey(n+1)? map.get(n+1): 0;
            int sum=left+right+1;
                map.put(n,sum);
            res=Math.max(res,sum);
            
            map.put(n-left,sum);
            map.put(n+right,sum);
        }
          
        }
        return res;
    }
}