Evaluate Division LeetCode solution in C++

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class Solution {
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 public:
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  vector<double> calcEquation(vector<vector<string>> &equations, vector<double> &values,
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                              vector<vector<string>> &queries) {
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    map<string, vector<pair<string, double>>> graph;
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    map<string, double> dist;
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    map<string, bool> visited;
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    for (int i = 0; i < equations.size(); i++) {
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      if (graph.count(equations[i][0]) == 0) {
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        graph[equations[i][0]] = {};
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        visited[equations[i][0]] = false;
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        dist[equations[i][0]] = DBL_MAX;
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      }
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      if (graph.count(equations[i][1]) == 0) {
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        graph[equations[i][1]] = {};
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        dist[equations[i][0]] = DBL_MAX;
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      }
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      graph[equations[i][0]].push_back({equations[i][1], values[i]});
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      if (values[i] != 0)
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        graph[equations[i][1]].push_back({equations[i][0], 1 / values[i]});
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      else
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        graph[equations[i][1]].push_back({equations[i][0], -1});
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    }
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    vector<double> result;
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    for (int i = 0; i < queries.size(); i++) {
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      if (graph.count(queries[i][0]) == 0 || graph.count(queries[i][1]) == 0) {
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        result.push_back(-1);
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        continue;
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      }
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      if (queries[i][0] == queries[i][1]) {
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        result.push_back(1);
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        continue;
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      }
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      for (auto j : visited) visited[j.first] = false;
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      priority_queue<pair<double, string>, vector<pair<double, string>>,
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                     greater<pair<double, string>>>
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          pq;
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      dist[queries[i][0]] = 1;
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      ;
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      pq.push({1, queries[i][0]});
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      bool flag = false;
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      while (!pq.empty()) {
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        auto k = pq.top();
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        pq.pop();
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        visited[k.second] = true;
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        if (k.second == queries[i][1]) {
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          flag = true;
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          result.push_back(dist[k.second]);
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          break;
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        }
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        for (int j = 0; j < graph[k.second].size(); j++) {
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          if (!visited[graph[k.second][j].first]) {
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            dist[graph[k.second][j].first] = dist[k.second] * graph[k.second][j].second;
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            pq.push({dist[graph[k.second][j].first], graph[k.second][j].first});
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          }
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        }
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      }
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      if (!flag) result.push_back(-1);
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    }
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    return result;
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  }
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};