Evaluate Division

class Solution {
public:
    double dfs(string src,string dst,unordered_map<string,vector<pair<string,double>>> adjlist,set<string> vis)
    {

        if(vis.find(src)!=vis.end())
        {
             return -1.0;
        }
        if(src==dst)
        {
            return 1.0;
        }
        vis.insert(src);
        for(auto u:adjlist[src])
        {

            double tmp=dfs(u.first,dst,adjlist,vis);
            if(tmp!=-1.0)
            {
                return tmp*(u.second);
            }
        }
        return -1.0;
    }
    vector<double> calcEquation(vector<vector<string>>& equations, vector<double>& values, vector<vector<string>>& queries) {
        unordered_map<string,vector<pair<string,double>>> adjlist;
        set<string> node;

        for(int i=0;i<equations.size();i++)
        {
            auto u = equations[i];
            adjlist[u[0]].push_back({u[1],values[i]});
            adjlist[u[1]].push_back({u[0],(double)(1/values[i])});

            node.insert(u[0]);
            node.insert(u[1]);
        }
        vector<double> ans;
        for(auto q:queries)
        {
            set<string> vis;
            if(node.find(q[0])==node.end() || node.find(q[1])==node.end())
            {
                ans.push_back(-1);
            }
            else
            {
                ans.push_back(dfs(q[0],q[1],adjlist,vis));
            }
        }
        return ans;
    }
};