0767.cpp

class Solution {
    typedef pair<int, char> pic;

  public:
    string reorganizeString(const string &s) {
        priority_queue<pic> pq;
        int count[27] = {0};
        string res;

        for (char c : s)
            count[c & 0x1F]++;
        for (int i = 1; i <= 26; i++)
            if (count[i] > 0) pq.push({count[i], 'a' + i - 1});

        while (!pq.empty()) {
            const auto [cnt, c] = pq.top();
            pq.pop();
            if (pq.empty()) {
                if (cnt == 1)
                    return res + c;
                else
                    return "";
            } else {
                const auto [ocnt, oc] = pq.top();
                pq.pop();
                res += c, res += oc;
                if (cnt - 1) pq.push({cnt - 1, c});
                if (ocnt - 1) pq.push({ocnt - 1, oc});
            }
        }
        return res;
    }
};