c++ directed graph depth first search -

i attempting write method dfs method directed graph. right running segmentation fault, , unsure is. understand of directed graphs believe logic right... fresh set of eyes nice help.

here function:

void wdigraph::depth_first (int v) const {  static int fvertex = -1; static bool* visited = null;  if( fvertex == -1 ) {    fvertex = v;    visited = new bool[size];    for( int x = 0; x < size; x++ ) {       visited[x] = false;    } }  cout << label[v]; visited[v] = true;  (int v = 0; v < adj_matrix.size(); v++) {    for( int x = 0; x < adj_matrix.size(); x++) {      if( adj_matrix[v][x] != 0 && visited[x] != false ) {         cout << " -> ";         depth_first(x);      }      if ( v == fvertex ) {         fvertex = -1;         delete [] visited;         visited = null;      }    } } } 

class definition:

class wdigraph { public: wdigraph(int =no_nodes);          // default constructor ~wdigraph() {};                   // destructor int get_size() { return size; }   // returns size of digraph  void depth_first(int) const;// traverses graph using depth-first search void print_graph() const;   // prints adjacency matrix of digraph  private: int size;                         // size of digraph vector<char> label;               // node labels vector< vector<int> > adj_matrix; // adjacency matrix }; 

thanks!

there few things might want consider. first function level static variables not idea, can redesign , make either regular variables (at cost of allocations) or instance members , keep them alive.

the function assumes adjacency matrix square, initialization code not shown, should checked. assumption can removed making inner loop condition adj_matrix[v].size() (given node v) or else if invariant, add assert before inner loop: assert( adj_matrix[v].size() == adj_matrix.size() && "adj_matrix not square!" ); --the same goes member size , size of adj_matrix self.

the whole algorithm seems more complex should, dfs starting @ node v has general shape of:

dfs( v )    set visited[ v ]    operate on node (print node label...)    each node reachable v:       if not visited[ node ]:          dfs( node ) 

your algorithm seems (incorrectly way) transversing graph in opposite direction. set given node visited, , try locate node start point of edge node. is, instead of following nodes reachable v, trying nodes v reachable. if case (i.e. if objective printing paths converge in v) must careful not hit same edge twice or end in infinite loop -> stackoverflow.

to see end stackoverlow, consider example. start node 1. create visited vector , mark position 1 visited. find there edge (0,1) in tree, , triggers if: adj_matrix[0][1] != 0 && visited[1], enter recursively start node being 1 again. time don't construct auxiliary data, remark visited[1], enter loop, find same edge , call recursively...