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.

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.

位操作

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;}