DFS --- Depth First Search 深度优先搜索算法

Depth First Search 

                   原理还是去看《DSAA》，这里着重分析实现策略。

如果对于图这种数据结构不熟悉，这个BFS一般是搞不定的...

下面分别是无向图的邻接表实现和邻接矩阵实现

http://blog.csdn.net/cinmyheart/article/details/41381845

http://blog.csdn.net/cinmyheart/article/details/41370465

－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－

/************************************************************
code file	: dfs.h
code writer	: EOF
code date	: 2014.11.22
e-mail		: [email protected]

code description:
	This file is a header file for out test program.
We abstract the data structure -- Graph here. And we also
declare some useful API to construct out naive graph :)

************************************************************/

#ifndef _DFS_H_
#define _DFS_H_

	#include <stdio.h>
	#include <stdlib.h>

	#define CONNECTED    1
	#define DISCONNECTED 0

	#define SUCCESS  0
	#define FAILED  -1

	#define UN_VISITED 0
	#define VISITED   1

	#define ENTRY_POINT 3

	struct visited
	{
		int array[0];
	};

	struct vertex
	{
		int value;
		struct vertex* next;
		struct vertex* end;
	};

	struct graph
	{
		int num_vertex;
		int num_edge;
		struct vertex adjacent[0];
	};


	void dfs(struct graph* p_graph,struct vertex* p_vertex,struct visited* p_visited);

	struct graph* init_graph(int vertex,int edge);
	void   release_graph(struct graph* p_graph);
	
	int add_edge(struct graph* p_graph,char from_v,char to_v);
	int print_graph(struct graph* p_graph);

#endif

关键的，对于DFS的实现

这个函数我设计接受三个参数(指针)，p_graph指向图，p_vertex指向节点,p_visited指向标记“数组”(动态分配得的结构体)

/*********************************************************
code writer	:	EOF
code date 	: 	2014.11.24
code file	:	dfs.c
e-mail		:	[email protected]

Code description:
	This function @dfs() is a implementation of 
"Depth first search" which is based on recursion.

**********************************************************/

#include "dfs.h"

void dfs(struct graph* p_graph,struct vertex* p_vertex,struct visited* p_visited)
{
	if(!p_vertex)
	{
		return;
	}

	p_visited->array[p_vertex->value] = VISITED;

	printf("%d->",p_vertex->value);

	for(p_vertex = p_vertex->next;
	   !!p_vertex;
	   p_vertex = p_vertex->next)
	{
		if(p_visited->array[p_vertex->value] == UN_VISITED)
		{
			dfs(p_graph,&(p_graph->adjacent[p_vertex->value]),p_visited);
		}
	}
	printf("\n");
}

那么我们使可以利用圈图进行测试的

比方说

节点链接是个圈：　1->2->3->4->1，这种，首尾相连的圈。

从任何节点进入，都可以停下并且检索完所有的节点。

我们的测试程序：

/****************************************************************
code file	: test_graph.c
code writer	: EOF
code date	: 2014.11.22
e-mail		: [email protected]

code description:
	Here , we use this program to call some API which would 
construct a ADT--graph and test it.

*****************************************************************/
#include "dfs.h"

int main()
{
	struct graph* p_graph = NULL;

	FILE* fp = fopen("./text.txt","r+");

	if(!fp)
	{
		printf("fopen() failed!\n");
		return 0;
	}

	int ret    = 0;
	int vertex = 0;
	int edge   = 0;

	int from_v = 0;
	int to_v   = 0;

	fscanf(fp,"%d",&vertex);
	fscanf(fp,"%d",&edge);

	p_graph = init_graph(vertex,edge);

	int temp = 0;
	for(temp = 0;temp < edge;temp++)
	{
		/*
		**	I think it's necessary to check the returned value
		** of scanf() family.
		*/
		ret = fscanf(fp,"%d %d",&from_v,&to_v);
		if(ret != 2)
		{
			break;
		}

		add_edge(p_graph,from_v,to_v);
	}

	struct visited* p_visited = 
	(struct visited*)malloc(sizeof(struct visited) +	sizeof(int)*(p_graph->num_vertex));

	for(temp = 0;temp < p_graph->num_vertex;temp++)
	{
		p_visited->array[temp] = UN_VISITED;
	}	

	print_graph(p_graph);

	/*
	**	Here, we start to DFS.
	*/
	dfs(p_graph,&(p_graph->adjacent[ENTRY_POINT]),p_visited);

	release_graph(p_graph);
	free(p_visited);
	p_visited = NULL;
	fclose(fp);
	return 0;
}

测试文本数据text.txt:

5
5
1 2
2 3
3 4
4 1

同样的，我们可以用其他的图进行测试：

测试文本：

８个节点，１２条边的图

8
12
3 6
3 1
1 4
1 2
4 3
4 6
4 7
4 5
7 6
2 4
2 5
5 7