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.

Example 1: Given ["abcw", "baz", "foo", "bar", "xtfn", "abcdef"] Return 16 The two words can be "abcw", "xtfn".

Example 2: Given ["a", "ab", "abc", "d", "cd", "bcd", "abcd"] Return 4 The two words can be "ab", "cd".

Example 3: Given ["a", "aa", "aaa", "aaaa"] Return 0 No such pair of words.

Solution

public class Solution {

    public int maxProduct(String[] words) {
        if(words == null || words.length < 2) return 0;
        int hash[] = new int[words.length];
        for(int i = 0; i < words.length; i++) {
            for(int k = 0; k < words[i].length(); k++) {
                hash[i] |= 1 << (words[i].charAt(k) - 'a');
            }
        }

        int max = 0;
        for(int i = 0; i < words.length; i++) {
            for(int j = i + 1; j < words.length; j++) {
                if((hash[i] & hash[j]) == 0) {
                    max = Integer.max(words[i].length() * words[j].length(), max);
                }
            }
        }
        return max;
    }

}