Given a string array words, find the maximum value of length(word[i]) * length(word[j]) where the two words do not share common letters. You may assume that each word will contain only lower case letters. If no such two words exist, return 0.

public class Solution {
    public int maxProduct(String[] words) {
        if (words == null || words.length == 0) return 0;

        int[] mask = new int[words.length];
        for (int i = 0; i < words.length; i++) {
            for (int j = 0; j < words[i].length(); j++) {
                mask[i] |= 1 << (words[i].charAt(j) - 'a');
            }
        }
        int result = 0;
        for (int i = 0; i < words.length; i ++) {
            for (int j = 1; j < words.length; j++) {
                if ((mask[i] & mask[j]) == 0) {
                    result = Math.max(result, words[i].length() * words[j].length());
                }
            }
        }
        return result;
    }
}

class Solution(object):
    def maxProduct(self, words):
        """
        :type words: List[str]
        :rtype: int
        """
        if not words:
            return 0

        ord_map = {}
        for word in words:
            mask = 0
            for c in set(word):
                mask |= (1 << (ord(c) - ord("a")))
            ord_map[mask] = max(ord_map.get(mask, 0), len(word))
        return max([ord_map[x] * ord_map[y] for x in ord_map for y in ord_map if not x & y] or [0])