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

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

// } Driver Code Ends
class Solution {
  private:
    bool detect(int src,vector<int> adj[],vector<int> &vis)
    {
        vis[src]=1;
        queue<pair<int,int>> q;
        q.push({src,-1});
        while(!q.empty())
        {
            int node = q.front().first;
            int parent = q.front().second;
            q.pop();
            for(int adjacent : adj[node])
            {
                if(!vis[adjacent])
                {
                    vis[adjacent]=1;
                    q.push({adjacent,node});
                }
                else if(parent!= adjacent)return true;
            }
        }
        return false;
    }
  public:
    // Function to detect cycle in an undirected graph.
    bool isCycle(int V, vector<int> adj[]) {
        vector<int> vis(V,0);
        for(int i = 0;i<V;i++)
        {
            if(!vis[i])
            {
                if(detect(i,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

//Submission made on GFG