Method dfs

LexicographicalNumbers.java:11–22

(int curNum, int target, List<Integer>res)

        return res;
    }
    public void dfs(int curNum, int target, List<Integer>res){
        if(curNum>target){
            return;
        }
        res.add(curNum);
        for(int d=0;d<10;d++){
            if(curNum*10+d>target){
                break;
            }
            dfs(curNum*10+d,target,res);
        }
    }
}