今天给大家说下图的广度优先遍历（BFS）：

    图的广度优先搜索是树的按层次遍历的推广，它的基本思想是：首先访问初始点vi，并将其标记为已访问过，接着访问vi的所有未被访问过的邻接点 vi1,vi2, …, vi t，并均标记已访问过，然后再按照vi1,vi2, …, vi t的次序，访问每一个顶点的所有未被访问过的邻接点，并均标记为已访问过，依次类推，直到图中所有和初始点vi有路径相通的顶点都被访问过为止。

如图：

 

       首先发下用邻接链表法实现的广度优先遍历代码（如果不理解邻接链表法，请在本博客数据结构系列中查找，里面有详细介绍），代码是基于本博客数据结构系列讲解邻接链表法实现图写的，大家可以把这段代码加在那些代码中就可以运行：：

static void recursive_bfs(TLGraph* tGraph, int v, int visited[], LGraph_Printf* pFunc)
{
	LinkQueue* queue = LinkList_Create();
	
	if(NULL != queue)
	{
		LinkQueue_Append(queue, tGraph->v + v);
		
		while(0 < LinkQueue_Length(queue))
		{
			int i = 0;
			
			v = (LVertex**)LinkQueue_Retrieve(queue) - tGraph->v;
			
			pFunc(tGraph->v[v]);
			
			printf(", ");
			
			for(i=0; i<tGraph->la[v]; i++)
			{
				TListNode* node = (TListNode*)LinkList_Get(tGraph->la[v], i);
				
				if(!visited[node->v])
				{
					LinkQueue_Append(queue, tGraph->v + node->v);
					
					visited[node->v] = 1;
				}
			}
		}
	}
	
	LinkQueue_Destroy(queue);
}

void LGraph_BFS(LGraph* graph, int v, LGraph_Printf* pFunc)
{
	TLGraph* tGraph = (TLGraph*)graph;
	
	int* visited = NULL;
	
	int condition = (NULL != tGraph);
	condition = condition && (0 <= v) && (v < tGraph->count);
	condition = condition && (NULL != pFunc);
	condition = condition && (NULL != (visited = (int*)calloc(tGraph->count, sizeof(int))));
	
	if(condition)
	{
		int i = 0;
		
		recursive_bfs(tGraph, v, visited, pFunc);
		
		for(i=0; i<tGraph->count; i++)
		{
			if(!visited[i])
			{
				recursive_bfs(tGraph, i, visited, pFunc);
			}
		}
		
		printf("\n");
	}
	
	free(visited);
}

 

最后发下用邻接矩阵法实现的广度优先遍历代码（如果不理解邻接矩阵法，请在本博客数据结构系列中查找，里面有详细介绍），代码是基于本博客数据结构系列讲解邻接矩阵法实现图写的，大家可以把这段代码加在那些代码中就可以运行：    

static void recursive_bfs(TMGraph* tGraph, int v, int visited[], MGraph_Printf* pFunc)
{
	LinkQueue* queue = LinkQueue_Create();
	
	if(NULL != queue)
	{
		LinkQueue_Append(queue, tGraph->v + v);
		
		visited[v] = 1;
		
		while(0 < LinkQueue_Length(queue))
		{
			int i = 0;
			
			v = (MVertex**)LinkQueue_Retrieve(queue) - tGraph->v;
			
			pFunc(tGraph->v[v]);
			
			printf(", ");
			
			for(i=0; i<tGraph->count; i++)
			{
				if((0 != tGraph->matrix[v][i]) && (!visited[i]))
				{
					LinkQueue_Append(queue, tGraph->v + i);
					
					visited[i] = 1;
				}
			}
		}
	}
	
	LinkQueue_Destroy(queue);
}

void MGraph_BFS(MGraph* graph, int v, MGraph_Printf* pFunc)
{
	TMGraph* tGraph = (TMGraph*)graph;
	
	int* visited = NULL;
	
	int condition = (NULL != tGraph);
	condition = condition && (0 <= v) && (v < tGraph->count);
	condition = condition && (NULL != pFunc);
	condition = condition && (NULL != (visited = (int*)calloc(tGraph->count, sizeof(int))));
	
	if(condition)
	{
		int i = 0;
		
		recursive_bfs(tGraph, v, visited, pFunc);
		
		for(i=0; i<tGraph->count; i++)
		{
			if(!visited[i])
			{
				recursive_bfs(tGraph, i, visited, pFunc);
			}
		}
		
		printf("\n");
	}
	
	free(visited); 
}