Maximum Product of Word Lengths

Given a string arraywords, find the maximum value oflength(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"]
Return16
The two words can be"abcw", "xtfn".

Example 2:

Given["a", "ab", "abc", "d", "cd", "bcd", "abcd"]
Return4
The two words can be"ab", "cd".

Example 3:

Given["a", "aa", "aaa", "aaaa"]
Return0
No such pair of words.