318. Maximum Product of Word Lengths.cpp

class Solution {
public:
    int maxProduct(vector<string>& words) {
        vector<int> mask(words.size());
        int ans = 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]) == 0)
                    ans = max(ans, int(words[i].length()*words[j].length()));
            }
        }
        return ans;
    }
};