Solution.cpp

class Solution {
public:
    string longestDiverseString(int a, int b, int c) {
        using pci = pair<char, int>;
        auto cmp = [](pci x, pci y) { return x.second < y.second; };
        priority_queue<pci, vector<pci>, decltype(cmp)> pq(cmp);

        if (a > 0) pq.push({'a', a});
        if (b > 0) pq.push({'b', b});
        if (c > 0) pq.push({'c', c});

        string ans;
        while (!pq.empty()) {
            pci cur = pq.top();
            pq.pop();
            int n = ans.size();
            if (n >= 2 && ans[n - 1] == cur.first && ans[n - 2] == cur.first) {
                if (pq.empty()) break;
                pci nxt = pq.top();
                pq.pop();
                ans.push_back(nxt.first);
                if (--nxt.second > 0) {
                    pq.push(nxt);
                }
                pq.push(cur);
            } else {
                ans.push_back(cur.first);
                if (--cur.second > 0) {
                    pq.push(cur);
                }
            }
        }

        return ans;
    }
};