数据结构（十四）：广度优先搜索

作用：搜索start顶点到与其邻接的各顶点的跳数

头文件：

root@ubuntu:/mnt/shared/appbox/graph# cat bfs.h 
#ifndef BFS_H
#define BFS_H

#include "graph.h"
#include "list.h"

typedef struct BfsVertex_
{
        void *data;
        VertexColor color;
        int hops;
}BfsVertex;

int bfs(Graph *graph, BfsVertex *start, List *hops);

#endif

接口：

int bfs(Graph *graph, BfsVertex *start, List *hops)
{
        Queue queue;
        AdjList *adjlist, *clr_adjlist;
        BfsVertex *clr_vertex, *adj_vertex;
        ListElmt *element, *member;

        for(element = list_head(&graph_adjlists(graph)); element != NULL; element = list_next(element))
        {
                clr_vertex = ((AdjList *)list_data(element))->vertex;
                if(graph->match(clr_vertex, start))
                {
                        clr_vertex->color = gray;
                        clr_vertex->hops = 0;
                }
                else
                {
                        clr_vertex->color = white;
                        clr_vertex->hops = -1;
                }
        }

        queue_init(&queue, NULL);
        if(graph_adjlist(graph, start, &clr_adjlist)!=0)
        {
                queue_destroy(&queue);
                return -1;
        }

        if(queue_enqueue(&queue, clr_adjlist)!=0)
        {
                queue_destroy(&queue);
                return -1;
        }

        while(queue_size(&queue) > 0)
        {
                adjlist = queue_peek(&queue);

                for(member = list_head(&adjlist->adjacent); member != NULL; member = list_next(member))
                {
                        adj_vertex = list_data(member);

                        // adjlist is null
                        if(graph_adjlist(graph, adj_vertex, &clr_adjlist)!=0)
                        {
                                queue_destroy(&queue);
                                return -1;
                        }

                        clr_vertex = clr_adjlist->vertex;

                        if(clr_vertex->color == white)
                        {
                                clr_vertex->color = gray;
                                clr_vertex->hops = ((BfsVertex *)adjlist->vertex)->hops + 1;

                                if(queue_enqueue(&queue, clr_adjlist)!=0)
                                {
                                        queue_destroy(&queue);
                                        return -1;
                                }
                        }
                }

                if(queue_dequeue(&queue, (void **)&adjlist)==0)
                {
                        ((BfsVertex *)adjlist->vertex)->color = black;
                }
                else
                {
                        queue_destroy(&queue);
                        return -1;
                }
        }

        queue_destroy(&queue);

        list_init(hops, NULL);

        for(element = list_head(&graph_adjlists(graph)); element != NULL; element = list_next(element))
        {
                clr_vertex = ((AdjList *)list_data(element))->vertex;
                if(clr_vertex->hops != -1)
                {
                        if(list_ins_next(hops, list_tail(hops), clr_vertex)!=0)
                        {
                                list_destroy(hops);
                                return -1;
                        }
                }
        }
        return 0;
}