图的广度优先搜索遍历根树的层次遍历类似

首先访问其实顶点v，然后选取与v邻接的全部顶点w0,w1,w2……进行访问，再依次访问与w0,w1,w2……..邻接的所有顶点，依此类推

也就是说用到一个队列

首先让一个顶点入队

如果队列不空的话：出对，依次检查出对顶点的所有邻接顶点，访问没有被访问过的邻接顶点并将其入队

队列为空：跳出循环

void BFS(AGraph G, int v, int visit[MAX_VERTEX_NUM])
{
	ArcNode *p;
	int que[MAX_VERTEX_NUM], front = 0, rear = 0;
	int j;
	cout << v << " ";
	visit[v] = 1;
	rear = (rear + 1) % MAX_VERTEX_NUM;
	que[rear] = v;
	while (front != rear)
	{
		front = (front + 1) % MAX_VERTEX_NUM;
		j = que[front];
		p = G.adjlist[j].firstarc;
		while (p)
		{
			if (visit[p->adjvex] == 0)
			{
				cout << p->adjvex;
				visit[p->adjvex] = 1;
				rear = (rear + 1) % MAX_VERTEX_NUM;
				que[rear] = p->adjvex;
			}
			p = p->nextarc;
		}
	}
}