/**

*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.

*/

class Solution {

public:

int maxProduct(vector<string>& words) {

vector<int> mask(words.size());

int result = 0;

for (int i=0; i<words.size(); ++i)

{

for (char c : words[i])

mask[i] |= 1 << (c - 'a');

for (int j=0; j<i; ++j)

if (!(mask[i] & mask[j]))

result = max(result, int(words[i].size() * words[j].size()));

}

return result;

}

};