topological sort using kahns algorithm

// { Driver Code Starts
#include <bits/stdc++.h>
using namespace std;

 // } Driver Code Ends



class Solution
{
    public:
    //Function to return list containing vertices in Topological order.
    void dfs(int src,bool *v,vector<int> &result,vector<int> adj[]){
        v[src]=true;
        for(auto node:adj[src])
            if (v[node]==false){
                dfs(node,v,result,adj);
            }
       result.push_back(src);
    }

    vector<int> topoSort(int V, vector<int> adj[])
    {
        // code here
        bool v[V]={false};
        vector<int> result;
        for(int i=0;i<V;++i)
                if (v[i]==false)
                     dfs(i,v,result,adj);
       reverse(result.begin(),result.end());
       return result;

    }
};

// { Driver Code Starts.

/*  Function to check if elements returned by user
*   contains the elements in topological sorted form
*   V: number of vertices
*   *res: array containing elements in topological sorted form
*   adj[]: graph input
*/
int check(int V, vector <int> &res, vector<int> adj[]) {
    vector<int> map(V, -1);
    for (int i = 0; i < V; i++) {
        map[res[i]] = i;
    }
    for (int i = 0; i < V; i++) {
        for (int v : adj[i]) {
            if (map[i] > map[v]) return 0;
        }
    }
    return 1;
}

int main() {
    int T;
    cin >> T;
    while (T--) {
        int N, E;
        cin >> E >> N;
        int u, v;

        vector<int> adj[N];

        for (int i = 0; i < E; i++) {
            cin >> u >> v;
            adj[u].push_back(v);
        }

        Solution obj;
        vector <int> res = obj.topoSort(N, adj);

        cout << check(N, res, adj) << endl;
    }

    return 0;
}  // } Driver Code Ends