Prerequisite Tasks

//checking for circle in directed graph
bool ans=true;
void dfs(vector <int> adj[],int i,bool visited[],bool dfs_visited[]){
    visited[i]=true;
    dfs_visited[i]=true;
    for(auto itr:adj[i]){
            if(visited[itr] && dfs_visited[itr]){ans=false; return;}
            if(!visited[itr])
            dfs(adj,itr,visited,dfs_visited);
    }
    dfs_visited[i]=false;
}
class Solution {
public:
    bool isPossible(int n, vector<pair<int, int> >& pre) {
       ans=true;
       vector<int> adj[n];
       for(auto itr:pre){
           adj[itr.second].push_back(itr.first);
       }
       bool visited[n],dfs_visited[n];
       memset(visited,false,sizeof(visited));
       memset(dfs_visited,false,sizeof(dfs_visited));
       for(int i=0;i<n;i++){
           if(!visited[i]){
               dfs(adj,i,visited,dfs_visited);
           }
       }
       return ans;

    }
};