Find Servers That Handled Most Number of Requests LeetCode solution in C++

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class Solution {
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 public:
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  vector<int> busiestServers(int k, vector<int> &arrival, vector<int> &load) {
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    int n = (int)arrival.size();
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    set<int> freeServers;
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    for (int i = 0; i < k; i++) freeServers.insert(i);
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    vector<int> serverTaskCount(k, 0);
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    set<pair<int, int>> workingServers; // [end time, server index]
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    for (int i = 0; i < n; i++) {
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      int startTime = arrival[i];
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      while (!workingServers.empty() && workingServers.begin()->first <= startTime) {
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        auto s = *workingServers.begin();
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        workingServers.erase(workingServers.begin());
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        freeServers.insert(s.second);
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      }
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      if (freeServers.empty()) continue;
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      int serverIndex = -1;
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      auto it = freeServers.lower_bound(i % k);
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      if (it == freeServers.end()) {
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        serverIndex = *freeServers.begin();
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        freeServers.erase(freeServers.begin());
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      } else {
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        serverIndex = *it;
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        freeServers.erase(it);
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      }
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      workingServers.insert({startTime + load[i], serverIndex});
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      serverTaskCount[serverIndex]++;
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      // printf("Task %d (%d, %d) assigned to server %d\n", i, startTime,
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      // load[i], serverIndex);
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    }
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    // for (auto x : serverTaskCount) cout << x << " ";
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    // cout << endl;
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    vector<int> ret;
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    int maxVal = *max_element(serverTaskCount.begin(), serverTaskCount.end());
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    for (int i = 0; i < k; i++)
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      if (maxVal == serverTaskCount[i]) ret.push_back(i);
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    return ret;
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  }
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};