图的BFS

每个顶点进队列一次，每条边处理一次，O(V+E)

public class BFS {

	public static void bfs(Graph g, Vertex v) {
		assert (true);
		Queue<Vertex> q = new LinkedList<Vertex>();
		q.add(v);
		v.color = Vertex.BLACK;
		q.add(new Vertex(-1));
		int flag = 0;
		Vertex c = null;
		while (!q.isEmpty()) {
			c = q.poll();
			if (c.id == -1) {
				System.out.println();
				if (flag == 0) {
					q.add(new Vertex(-1));
					flag++;
					continue;
				} else {
					break;
				}
			} else {
				System.out.print(c.id + " ");
				flag = 0;
			}
//			c.color = Vertex.BLACK;
			for(int i=0; i<g.count_vertex; i++){
				if(g.vertexs[i].color == Vertex.WHITE 
						&& g.adjMatrix[c.id][i] > 0){
					q.add(g.vertexs[i]);
					g.vertexs[i].color = Vertex.BLACK;
				}
			}
		}
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Graph g = Graph.createNoDirectedGraph(8, "dfs.txt");
//		Graph g = Graph.createDirectedGraph(8, "dfs.txt");
		g.printGraph();
		BFS.bfs(g, g.vertexs[0]);

	}

}