图的DFS

 每个节点访问一次，每条边访问一次，时间复杂度O(V+E)

public class DFS {
	public static int timer = 0;
	
	public static void dfs(Graph g, Vertex v){
		assert(true);
		if(v.color != Vertex.WHITE){
			return;
		}
		System.out.print(v.id + " ");
		v.color = Vertex.GRAY;
		v.start_time = timer++;
		for(int i=0; i<g.count_vertex; i++){
			if(g.adjMatrix[v.id][i] > 0){
				g.vertexs[i].parent = v;
				dfs(g, g.vertexs[i]);
			}
		}
		v.color = Vertex.BLACK;
		v.end_time = timer++;
	}
	

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		//如果是无向连通图，一次遍历可以读完,只有一棵树
		Graph g = Graph.createNoDirectedGraph(8, "dfs.txt");
		g.printGraph();

		DFS.timer = 0;
		DFS.dfs(g, g.vertexs[5]);
		System.out.println();
		for(int i=0; i<g.count_vertex; i++){
			System.out.print(g.vertexs[i].start_time + " " + g.vertexs[i].end_time + " : ");
		}
		System.out.println();
		for(int i=0; i<g.count_vertex; i++){
			System.out.print(g.vertexs[i].parent.id + " ");
		}
		System.out.println();
		//如果有向连通图，一次读不完，多次读，形成森林
//		Graph g = Graph.createDirectedGraph(8, "dfs.txt");
//		g.printGraph();

		
//		for(int i=0; i<g.count_vertex; i++){
//			if(g.vertexs[i].color == Vertex.WHITE){
//				DFS.dfs(g, g.vertexs[i]);
//			}
//		}
		
	}

}