318. Maximum Product of Word Lengths

public class Solution {
    public int maxProduct(String[] words) {
        int max = 0;
        //sort the array based on string length in a descending order.
        Arrays.sort(words, new Comparator<String>(){
           @Override
           public int compare(String a, String b)
           {
               return b.length() - a.length();
           }
        });
        
        //get the spectrum for each word.
        int[] spectrum = new int[words.length];
        
        for(int w = 0; w<words.length; ++w)
        {
            String word = words[w];
            for(int i = 0; i<word.length(); ++i)
            {
                spectrum[w] |= 1<<word.charAt(i) - ‘a‘;  //1<<32 <==> 1<<0. 32 is the cycle.
            }
        }
        
        for(int i = 0; i<words.length-1; ++i)
        {
            int l = words[i].length();
            if(l*l <= max)
                break;
            for(int j = i+1; j<words.length; ++j)
            {
                if((spectrum[i] & spectrum[j]) == 0)
                {
                    max = Math.max(max, l*words[j].length());
                    break;
                }
            }
        }
        return max;
    }
}