Graph-Algorithms/TopologicalSort.cpp at main · Alen-Scaria1516/Graph-Algorithms · GitHub

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/*
  Submission Made on GFG for the problem on Topological Sort
  https://www.geeksforgeeks.org/problems/topological-sort/1?itm_source=geeksforgeeks&itm_medium=article&itm_campaign=bottom_sticky_on_article
*/


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

// } Driver Code Ends
class Solution
{
    void dfs(int node,vector<bool>&vis,vector<int> adj[],stack<int>&s)
    {
        vis[node] = 1;
        for(int i : adj[node])
        {
           if(!vis[i]) dfs(i,vis,adj,s);
        }
        s.push(node);
    }

	public:
	//Function to return list containing vertices in Topological order.
	vector<int> topoSort(int V, vector<int> adj[])
	{
	    vector<bool> vis(V,0);
	    stack<int> s;
	    for(int i = 0;i<V;i++)
	    {
	        if(!vis[i])
	        {

	            dfs(i,vis,adj,s);
	        }
	    }
	    vector<int> ans;
	    while(!s.empty())
	    {
	        ans.push_back(s.top());
	        s.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