// Stephanie's class notes.
// sorely missing comments and docstrings. sorry.
// Graph implemented with adjacency list
// Note: I have implemented the graph as a digraph. If you want to connection
// node A to node B, it puts in an edge from A to B, but not the corresponding
// edge from B to A.
import java.util.*;
public class Graph1 {
    private ArrayList<GraphNode> nodes;
    
    public static class GraphNode {
        private ArrayList<GraphNode> neighbors;
        String label;
        boolean marked;
        
        public GraphNode() {
            this.neighbors = new ArrayList<GraphNode>();
            this.label = "";
            this.marked = false;
        }
        
        public GraphNode(String label) {
            this.neighbors = new ArrayList<GraphNode>();
            this.label = label;
            this.marked = false;
        }
        
        // make a directed connection from this node to the other node
        public void connectTo( GraphNode other ) {
            this.neighbors.add( other );
        }           
        
        public String toString() { 
            String ret = this.label + ":";
            for (GraphNode n: this.neighbors)
                ret += " " + n.label;
            return ret;
        } 
    } // end class GraphNode
    
    public Graph1() {
        nodes = new ArrayList<GraphNode>();   
    }
    
    public void connect( GraphNode fromNode, GraphNode toNode ) {
        if (! this.nodes.contains( fromNode ))
            this.nodes.add( fromNode );
        if (! this.nodes.contains( toNode ))
            this.nodes.add( toNode );
        fromNode.connectTo( toNode );
    }
    
    public void printAll() {
        for (GraphNode n: nodes)
            System.out.println( n );
    }
    
    public void generalTraversalPrint(GraphNode n0) {
        // unmark all nodes
        for (GraphNode n: nodes)
            n.marked = false;
        ArrayDeque<GraphNode> nbs = new ArrayDeque<GraphNode>();
        nbs.add( n0 );
        while (!nbs.isEmpty()) {
            GraphNode n = nbs.remove();
            n.marked = true;
            System.out.println( n );
            for (GraphNode p: n.neighbors) {
                if (!p.marked && !nbs.contains(p))
                    nbs.add( p );
            }
        }            
    }
    
    public static void main( String[] args ) {
        Graph1 g = new Graph1();
        GraphNode n1 = new GraphNode( "n1" );
        GraphNode n2 = new GraphNode( "n2" );
        GraphNode n3 = new GraphNode( "n3" );
        g.connect( n1, n2 );
        g.connect( n3, n2 );
        g.printAll();
        System.out.println( "Traversing from n1" );
        g.generalTraversalPrint( n1 );
        System.out.println( "Traversing from n2" );
        g.generalTraversalPrint( n2 );
        System.out.println( "Traversing from n3" );
        g.generalTraversalPrint( n3 );
    }
}