Hacktober_Repo_22/CPP/TopologicalSort.cpp at main · py3-coder/Hacktober_Repo_22 · GitHub

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

 // } Driver Code Ends
class Solution
{
	public:

	void topo(int i,stack<int> &st,vector<int> &vis,vector<int> adj[]){
	    vis[i]=1;

	    for(auto it:adj[i]){
	        if(!vis[it]){
	            topo(it,st,vis,adj);
	        }
	    }
	    st.push(i);
	}


	//Function to return list containing vertices in Topological order.
	vector<int> topoSort(int V, vector<int> adj[])
	{
	    stack<int> st;
	    vector<int> v(V+1,0);

	    int i=0;

	    while(i<V){
	        if(v[i]==0){
	            topo(i,st,v,adj);
	        }
	        i++;
	    }
	    i=0;
	    vector<int> ans;
	    while(!st.empty()){
	        ans.push_back(st.top());
	        st.pop();
	    }
	    return ans;
	}
};

// { 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[]) {

    if(V!=res.size())
    return 0;

    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