Get Watched Videos by Your Friends LeetCode solution in C++

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class Solution {
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 public:
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  vector<string> watchedVideosByFriends(vector<vector<string>> &watchedVideos,
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                                        vector<vector<int>> &friends, int id, int level) {
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    vector<vector<int>> graph(watchedVideos.size());
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    for (int i = 0; i != friends.size(); i++)
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      for (auto &f : friends[i]) graph[f].push_back(i), graph[i].push_back(f);
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    int tmp_level = 0;
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    vector<int> vis(watchedVideos.size(), 0);
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    vector<string> ans;
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    queue<int> q;
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    q.push(id);
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    while (!q.empty()) {
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      if (tmp_level++ == level) {
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        unordered_map<string, int> mp;
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        while (!q.empty()) {
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          int t = q.front();
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          q.pop();
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          if (vis[t]) continue;
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          vis[t] = 1;
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          for (auto &v : watchedVideos[t]) mp[v]++;
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        }
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        set<pair<int, string>> st;
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        for (auto &[s, n] : mp) st.insert({n, s});
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        for (auto &it : st) ans.push_back(it.second);
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      }
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      int n = q.size();
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      while (n--) {
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        int t = q.front();
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        q.pop();
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        if (vis[t]) continue;
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        vis[t] = 1;
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        for (auto &x : graph[t])
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          if (!vis[x]) q.push(x);
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      }
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    }
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    return ans;
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  }
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};