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