CC150 4.2

4.2 Given a directed graph, design an algorithm to find out whether there is a route between two nodes.

Node
{
  List<Node> neighbours;
}

boolean isConnected(Node from, Node to)
{
  Stack<Node> toVisit = initStack();
  Set<Node> seen = initSet();
  
  toVisit.push(from);
  
  while (!toVisit.isEmpty())
  {
    Node n = toVisit.pop();
    
    if (n == to)
      return true;
    
    while (Node neighbour : n.neighbours)
    {
      if (!seen.contains(neighbour))
      {
        seen.add(neighbour);
        toVisit.add(neighbour);
      }    
    }
  }
  
  return false;  
}