public int maxProduct(String[] words) {
        if(words==null || words.length<2) return 0;
        int[]arr=new int[words.length];
        int[]len=new int[words.length];
        for(int i=0;i<words.length;++i){
            arr[i]=toInt(words[i]);
            len[i]=words[i].length();
        }
        int max=0;
        for(int i=0;i<words.length;++i){
            for(int j=i+1;j<words.length;++j){
                if((arr[i]&arr[j])==0){
                   max=Math.max(max,len[i]*len[j]);
                }
            }
        }
        return max;
    }