main(){
graph **adj_list;
int n, m, n1, n2;
//Creating the adjacency list
scanf("%d %d", &n, &m);
adj_list=create_empty_list(adj_list, n);
//Creating edges
int i;
for(i=0;i<m;++i){
scanf("%d %d", &n1, &n2);
create_edge(n1,n2,adj_list,n);
create_edge(n2,n1,adj_list,n);
}
print_list(adj_list, n);
//Marking elements as visited
int *visited,*parent;
visited=(int *)malloc(n*sizeof(int));
parent=(int *)malloc(n*sizeof(int));
for(i=0;i<n;++i){
visited[i]=0;
parent[i]=-1;
}
//Printing the connected componenets
printf("\n\nThe cycles are: \n");
for(i=0;i<n;++i){
if(visited[i]==0){
dfs_cycle(adj_list,i,visited,parent);
}
}
}
bool dfs_cycle(vector<unordered_set<int>>& graph, int node, vector<bool>& onpath, vector<bool>& visited)
{
onpath[node] = visited[node] = true;
//go through the adjcent list for this node
for(int neigh : graph[node])
{
if (onpath[neigh] || dfs_cycle(graph, neigh, onpath, visited))
return true;
}
return onpath[node] = false;
}
void dfs_cycle(graph **adj, int x, int *visited, int *parent){
int id;//Temporarily store the id of element
graph *temp;//Loop variable
visited[x]=1;//Marking x as visited
//Parsing through all the neighbours of x
temp=adj[x]->next;
while(temp!=NULL){
id=temp->id;
if(visited[id]==0){
parent[id]=x;
dfs_cycle(adj,id,visited,parent);
}
else if(visited[id]==1&&parent[id]!=x)
//write statements for printing the cycle
temp=temp->next;
}
}
bool canFinish(int numCourses, vector<pair<int, int>>& prerequisites) {
//as the graph node value is int type, we use the node value to index
// the nodes, for non-int value, maybe key_to_index is needed
// also visited flags are accessed by node value
// visited = true does not mean the cycle is detected!!
// after all the adjacent nodes are dfsed, the onpath is set to
// false. then if the adjacent nodes is still onpath but now get
// to be dfsed, cycle is detected!!
//adjacent list is represneted by unordered_set<int>
vector<unordered_set<int>> graph = make_graph(numCourses, prerequisites);
vector<bool> onpath(numCourses, false), visited(numCourses, false);
//loop the vertices to perform DFS
for(int i = 0; i < numCourses; i++)
{
if (!visited[i] && dfs_cycle(graph, i, onpath, visited))
return false;
}
return true;
}
