c++ - Detecting and printing cycle in undirected graph -

i have question similar - same - one. want know how not detect cycle print out vertices cycle contains. tried ways mentioned in question above, must have done wrong, why doesn't work my. program checks if 1 specific vertex makes cycle. code here:

#include<iostream> #include <list> using namespace std;   class graph {     int v;         list<int> *adj;     public:     graph(int v);        void addedge(int v, int w);        bool graph::iscyclicutil(int v, bool visited[], int *cyclevertices, int parent, int index); };  graph::graph(int v) {     this->v = v;     adj = new list<int>[v]; }  void graph::addedge(int v, int w) {     adj[v].push_back(w);      adj[w].push_back(v); }   bool graph::iscyclicutil(int v, bool visited[], int *cyclevertices, int parent, int index) {      visited[v] = true;       list<int>::iterator i;     (i = adj[v].begin(); != adj[v].end(); ++i)     {          if (!visited[*i])         {             if (iscyclicutil(*i, visited, cyclevertices, v, index)) {                 if (index <= 1 || cyclevertices[0] != cyclevertices[index - 1])                     cyclevertices[index++] = *i;                 return true;             }         }          else if (*i != parent) {             cyclevertices[index++] = *i;             return true;         }     }     return false; }   int main() {     bool *visited = new bool[5];     (int = 0; < 5; i++)         visited[i] = false;     int cyclevertices[5];     (int = 0; < 5; i++)         cyclevertices[i] = -1;     graph g1(5);     g1.addedge(1, 0);     g1.addedge(0, 2);     g1.addedge(2, 1);     g1.addedge(0, 3);     g1.addedge(3, 4);     g1.iscyclicutil(4, visited, cyclevertices, -1, 0) ? cout << "graph contains cycle\n" :         cout << "graph doesn't contain cycle\n";     int x = 0;     while (cyclevertices[x] != -1)         cout << cyclevertices[x++] << " ";     return 0; } 

i've found solution. i've tried j_random_hacker's solution in post , didn't work. problem indexing in cyclevertices in code. variable index same. i've added new attribute index in class graph , works. here edited code:

#include<iostream> #include <list>  #define finished -1 #define nocycle -2 using namespace std;   class graph {     int v;        int index;     list<int> *adj;    public:     graph(int v);        void addedge(int v, int w);       void set_index();     int graph::iscyclicutil(int v, bool visited[], int *cyclevertices, int parent); };  graph::graph(int v) {     this->v = v;     adj = new list<int>[v];     this->index = 0; }  void graph::set_index() {     this->index = 0; }  void graph::addedge(int v, int w) {     adj[v].push_back(w);      adj[w].push_back(v);  }  int graph::iscyclicutil(int v, bool visited[], int *cyclevertices, int parent) {     visited[v] = true;      list<int>::iterator i;     (i = adj[v].begin(); != adj[v].end(); ++i)     {         if (!visited[*i])         {             int result = iscyclicutil(*i, visited, cyclevertices, v);             if (result == finished)                 return finished;             else if (result != nocycle) {                 cyclevertices[index++] = v;                 if (result == v)                     return finished;                 else                     return result;             }         }          else if (*i != parent) {             return *i;         }     }     return nocycle; }   int main() {     bool *visited = new bool[4];     (int = 0; < 4; i++)         visited[i] = false;     int cyclevertices[4];     (int = 0; < 4; i++)         cyclevertices[i] = -1;     graph g1(4);     g1.addedge(0, 1);     g1.addedge(1, 2);     g1.addedge(2, 3);     g1.addedge(3, 0);     g1.iscyclicutil(3, visited, cyclevertices, -1) ? cout << "graph contains cycle\n" :         cout << "graph doesn't contain cycle\n";     int x = 0;     while (cyclevertices[x] != -1)         cout << cyclevertices[x++] << " ";     return 0; }