318. 最大单词长度乘积

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位运算

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class Solution {
public:
    unsigned to_uword(const string &word) {
        unsigned res = 0;
        for (auto &&c: word) {
            res |= 1 << (c - 'a');
        }
        return res;
    }

    int maxProduct(vector<string>& words) {
        vector<unsigned> uwords;
        uwords.reserve(words.size());
        for (auto &&w: words) {
            uwords.push_back(to_uword(w));
        }
        
        int m = 0;
        int n = words.size();
        for (int i = 0; i < n; i++) {
            for (int j = i; j < n; j++) {
                auto &s1 = uwords[i];
                auto &s2 = uwords[j];
                if (s1 & s2) continue;
                if (int r = words[i].size() * words[j].size(); r > m) m = r;
            }
        }
        return m;
    }
};