Detec_Cycle_using_DFS.cpp

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

 // } Driver Code Ends



class Solution 
{
public:
    bool dfs(int node, int parent, vector<int> adj[], vector<int> &vis){
        vis[node] = 1;
        for(auto it: adj[node]){
            if(vis[it]==0){
                if (dfs(it,node,adj,vis)) return true;
            }else if(it != parent) return true;
        }
        return false;
    }
public:
    //Function to detect cycle in an undirected graph.
	bool isCycle(int V, vector<int>adj[])
	{
	    vector <int> vis(V+1,0);
        for(int i=0;i<V;i++){
            if(vis[i]!=0) 
            {
                if(dfs(V,-1,adj,vis)) return true;
            }
        return false;
	}
};

// { Driver Code Starts.
int main(){
	int tc;
	cin >> tc;
	while(tc--){
		int V, E;
		cin >> V >> E;
		vector<int>adj[V];
		for(int i = 0; i < E; i++){
			int u, v;
			cin >> u >> v;
			adj[u].push_back(v);
			adj[v].push_back(u);
		}
		Solution obj;
		bool ans = obj.isCycle(V, adj);
		if(ans)
			cout << "1\n";
		else cout << "0\n";
	}
	return 0;
}  // } Driver Code Ends