Maximum Product of Word Lengths

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.

• Time: O(n)
• Space: O(1)

public int maxProduct(String[] words) {
    int[] masks = new int[words.length];
    int max = 0;
    for (int i = 0; i < words.length; i++) {
        for (char c : words[i].toCharArray()) {
            masks[i] |= 1 << c - 'a';
        }
        for (int j = 0; j < i; j++) {
            if ((masks[i] & masks[j]) == 0) {
                max = Math.max(max, words[i].length() * words[j].length());
            }
        }
    }
    return max;
}