Course Schedule IV

class Solution {
public:
   vector<bool> checkIfPrerequisite(int n, vector<vector<int>>& prerequisites, vector<vector<int>>& queries) {
       vector<set<int>> cs(n+1);
       
       for(auto x: prerequisites)
           cs[x[0]].insert(x[1]);
       

       for(int i=0; i<=n; i++){
           for(auto x: cs[i])
               for(auto y: cs[x])
                   if(!cs[i].count(y))
                       cs[i].insert(y);
       }
       for(int i=0; i<=n; i++){
           for(auto x: cs[i])
               for(auto y: cs[x])
                   if(!cs[i].count(y))
                       cs[i].insert(y);
       }
       vector<bool> ans;
       for(auto x: queries){
           if(cs[x[0]].count(x[1]))
               ans.push_back(true);
           else
               ans.push_back(false);
       }
       
       return ans;
   }
};