Implementation of depth-first algorithm

Question

Hi, I am trying to implement depth-first algorithm.(directed graph, no loops). Here what I have so far.
//form a one-element stack with the root node.
Stack st=new st();
boolean goalflg=false;
st.push(?)//do I need to clone the value from the tree, if yes, how can I do this? Should it be a Spanning Tree or not?
//repeat until the first path in the stack terminates at the goal node or the stack is empty
while(st.size()!=null || goalflg == true){  
/*-remove the first math from the Stack;create new paths by extending the first path to all neighbors of the terminal node * /
int temp=st.pop();
nodeRight=tree.goRight();// I aren't sure nodeLeft=tree.goLeft();
//reject all new paths with loops (how can I do this?)
//if the goal is found-success, else -failure     
if (temp==goalNode)     
{goalflg=true;}     
else{        //add the new paths to the front of stack      
st.push(nodeRight);
st.push(nodeLeft);     
Please,please help!
Sincerely,
Byryndyk
P.S. I check out google, but it has mostly the theory about this method. What I am interested is how to make it alive.

Answer 1

This algorithm for DFS has no constraints on edges as it works purely by inspecting adjacency lists; if a directed edge, e, goes from vertex u to vertex v, then v is adjacent to u, but u is not adjacent to v i.e. you can not travel this edge from v to u.
     public VertexModelInterface[] depthFirstSearch(VertexModelInterface from)
          visited.add(from);
          VertexModelInterface[] adjacencyList = (VertexModelInterface[]) from.getAdjacencyList().toArray(new VertexModelInterface[0]);
          for (int index = 0; index < adjacencyList.length; index++)
               if (!visited.contains(adjacencyList[index]))
                    depthFirstSearch(adjacencyList[index]);
               } // end if
          } // end for
          return (VertexModelInterface[]) visited.toArray(new VertexModelInterface[0]);
     } // end depthFirstSearch
visited is a list containing vertices. Each vertex has an adjacency list containing references to adjacent vertices.
Hope this helps anyone whos looking for a neat recursive (implicit stack) implementation. I also have implementations for BFS, Cut-Edge-Detection and Fleury's algorithm.
Kind regards,
Darren Bishop.
[email protected]