Minimum Degree of a Connected Trio in a Graph LeetCode solution in C++

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class Solution {
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 public:
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  int minTrioDegree(int n, vector<vector<int>> &edges) {
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    vector<unordered_set<int>> adj(n + 1);
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    int res = INT_MAX;
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    for (vector<int> &edge : edges) {
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      adj[edge[0]].insert(edge[1]);
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      adj[edge[1]].insert(edge[0]);
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    }
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    for (int i = 1; i < n; ++i) {
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      for (auto iter1 = adj[i].begin(); iter1 != adj[i].end(); ++iter1) {
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        if (*iter1 <= i) continue;
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        for (auto iter2 = adj[i].begin(); iter2 != adj[i].end(); ++iter2) {
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          int u = *iter1, v = *iter2;
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          if (v <= u) continue;
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          if (adj[u].count(v)) {
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            int cur = adj[i].size() + adj[u].size() + adj[v].size() - 6;
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            res = min(res, cur);
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          }
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        }
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      }
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    }
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    return res == INT_MAX ? -1 : res;
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  }
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};