Graph theory-topological ordering of a direction graph

(1), directed to the graph, the side is a direction.
Adjacency matrix representation method Upper and lower triangles are asymmetrical. To add a side is to just one statement,
Add an Edge
public void Addedge (int start,int end) {
Adjmat[start][end] = 1;
}


(2), the algorithm of the direction graph-topology sorting
In the application of a direction graph, some items or events must be sorted or occurred in a particular order.
College courses, for example, require the required courses to get a degree. Each year, the curriculum is sorted according to the order, all compulsory, finally can reply, get a degree.
Steps for topology sorting:
(1), find a no successor vertex (if there is a side from a to point B, then B is a successor).
(2), remove this vertex from the diagram, and insert the vertex mark before the list.
(3), repeat steps 1 and 2. Until all vertices are removed from the diagram. The order of vertices displayed in the list is the result of the topology ordering.

Ring: Loop diagram is not a topological order, if there are n vertices of the graph has more than N-1 edge, then there must be a ring.

Graph_topo.java

Package com.mapbar.structure; /** * * Class graph_topo * * Description topological ordering of the graph * * Company Mapbar * * Author CHENLL
	
	OM * * Version 1.0 * * Date 2011-11-17 03:38:27//Define node Class vertex{public char label;
	
	public Boolean isvisited;
		Public Vertex (char label) {this.label = label;
	this.isvisited = false;
	
	} public class Graph_topo {//vertex array private vertex[] Varr;
	
	 Define adjacency matrix private int[][] Adjmat; 
    
     Maximum number of vertices private int maxSize;
    
    The current vertex subscript private int currvertex;
    
    Private char[] Sortedarr;
    	Construction method Public Graph_topo (int maxSize) {Sortedarr = new char[maxsize];
    	This.maxsize = maxSize;
    	Varr = new Vertex[maxsize];
    	Adjmat = new Int[maxsize][maxsize];
    		for (int i = 0; i<adjmat.length; i++) {for (int j = 0; j<adjmat.length; j + +) {Adjmat[i][j] = 0;
    } Currvertex = 0;
    //Add a vertex public void Addvertex (char label) {	varr[currvertex++] = new Vertex (label);
    //Add one edge public void Addedge (int start,int end) {Adjmat[start][end] = 1;
    //Display a vertex public void Disvertex (int v) {System.out.print (varr[v].label+ ",");
	   }//topology sort public void topo () {int orig_nvert = Currvertex;
		   while (currvertex>0) {int cuvertex = NOSUC ();
			   if (currvertex==-1) {System.out.println ("There are loops in the diagram, cannot be sorted by topology");
		   Return
		   } sortedarr[currvertex-1] = Varr[cuvertex].label;
	   Deletevertex (Cuvertex);
   } Disallvertex (Orig_nvert);
	   ///Find a no successor node public int nosuc () {Boolean isedge;
		   for (int i = 0; i<currvertex; i++) {Isedge = false;
				   for (int j = 0; j<currvertex; j + +) {if (adjmat[i][j]>0) {Isedge = true;
			   Break
		   } if (!isedge) {return i;
   }} return-1; ///delete vertices, the following vertices move forward while rows and columns are removed from the matrix, and the rows below and to the right column public void Deletevertex (int delv) {if Delv!=CURRVERTEX-1) {///delete vertex for (int j = Delv; j<currvertex; j +) {Varr[j] = varr[j+1]; //delete Vertex's adjacency matrix//Move up for (int row = Delv; row<currvertex-1; row++) {for (int col = 0; col<c
			   urrvertex;col++) {Adjmat[row][col] = Adjmat[row+1][col]; }//left for (int col = Delv; col<currvertex-1; col++) {for (int row = 0; Row<currvertex;ro
			   w++) {Adjmat[row][col] = adjmat[row][col+1];
   }} currvertex--; }//Display topology sort results public void Disallvertex (int org_length) {for (int j = 0; j<org_length; j + +) {System.out.print (
		Sortedarr[j]+ ",");
    	}//Keynote function public static void main (string[] args) {Graph_topo g = new Graph_topo (10);
    	G.addvertex (' a ');
    	G.addvertex (' B ');
    	G.addvertex (' C ');
    	G.addvertex (' d ');
    	G.addvertex (' e ');   	
    	G.addvertex (' f ');
    	G.addedge (0,1);
    	G.addedge (0,2);
    	G.addedge (1,3);
    	G.addedge (4,5); G.Addedge (5,1);
    G.topo ();
 }
}

Output

E,f,a,b,d,c,