DFS--圖中兩點之間的路徑

# include <stdio.h>
# include <memory.h>
# include <malloc.h>
# define MAX 20			//最大頂點數 


typedef struct VNODE
{
	int num;		//該邊所指的頂點的位置 
	struct VNODE *next;		//指向下一條邊的指針 
}arcnode;		//表的結點 

typedef struct LIST
{
	char data;		//頂點信息 
	arcnode * firstarc ;		//指向第一條依附頂點的邊和弧指針 
}ADJVEX[MAX];		//頭結點 

typedef struct ALGRAPH
{
	ADJVEX vertices;
	bool visited[MAX];		//訪問標誌數組 
	int vexnum,arcnum;		//圖的當前頂點數和弧數 
}algraph;

void init_algraph (algraph &g)		//初始化圖 
{
	memset(g.visited,false,sizeof(bool)*MAX);		//訪問標誌數組置false，表示未訪問 
	g.arcnum = 0;
	g.vexnum = 0;
}

int locatenode(algraph &g,char ch)		//定位ch在頂點向量中的位置 
{
	int i;
	for (i=0;i<g.vexnum && ch != g.vertices[i].data;++i)
	;
	
	return i;
}

void add_vex (algraph &g)		//增加頂點 
{
	printf ("請輸入頂點個數\n");
	scanf ("%d",&g.vexnum);
	printf ("請輸入頂點信息\n");
	for (int i=0;i<g.vexnum;++i)
	{
		scanf (" %c",&g.vertices[i].data);		//構造頂點向量 
		g.vertices[i].firstarc = NULL; 
	}
}

void add_arc(algraph &g)		//增加邊 
{
	arcnode *s,*p,*t;
	printf ("請輸入邊的個數\n");
	scanf ("%d",&g.arcnum);
	printf ("請輸入邊的信息\n");
	char ch1,ch2;
	for (int k=0;k<g.arcnum;++k)
	{
		scanf (" %c %c",&ch1,&ch2);
		int i = locatenode(g,ch1);
		int j = locatenode(g,ch2);		//確定ch1，ch2在頂點向量的位置 
		s = (arcnode *)malloc(sizeof(VNODE));
		t = (arcnode *)malloc(sizeof(VNODE));
		
		
		s->num = j;			//該邊所指向的位置爲j 
		s->next = NULL;
		if (!g.vertices[i].firstarc)
			g.vertices[i].firstarc = s;
		else
		{
			for (p=g.vertices[i].firstarc; p->next; p=p->next)
			;
			p->next = s;
		}
		
		t->num = i;			//該邊所指向的位置爲i 
		t->next = NULL;
		if (!g.vertices[j].firstarc)
			g.vertices[j].firstarc = t;
		else
		{
			for (p=g.vertices[j].firstarc; p->next; p=p->next)
			;
			p->next = t;
		}
	}
}

void creat_algraph(algraph &g)		//構造鄰接鏈表 
{
	add_vex(g);
	add_arc(g);
}

void print_algraph (algraph &g)		//輸出圖 
{
	int i; 
	arcnode *p;
	printf ("編號			頂點				鄰接結點\n");
	for (i=0; i<g.vexnum; ++i)
	{
		printf ("%d			%c				",i,g.vertices[i].data);
		for (p=g.vertices[i].firstarc; p; p=p->next)
		{
			printf (" %d ",p->num);
		}
		
		printf ("\n");
	}
}

void visit(algraph &g,int i)
{
	printf ("%c ",g.vertices[i].data);
	g.visited[i] = true;
}

void DFStraverse(algraph &g,int i)		//深度優先搜索 
{										//從第i個開始搜索 
	visit(g,i);
	arcnode *p;
	for (p=g.vertices[i].firstarc; p; p=p->next)
	{
		if (!g.visited[p->num])
		{
			DFStraverse(g,p->num);
		}
	}
}

void DFSearch(algraph &g,int i,int s,char path[])
{
	arcnode *p;
	g.visited[i] = true;
	static int found = 0;
	static int rear = 0;		//路徑數組的尾指針 
	path[rear++] = g.vertices[i].data;
	path[rear] = '\0';
	for (p=g.vertices[i].firstarc; p && !found; p=p->next)
	{
		if (s == p->num)		//找的目標結點 
		{
			found = 1;		//foun置1，退出 
			path[rear++] = g.vertices[p->num].data;
			path[rear] = '\0';
		}
		else if (!g.visited[p->num])
			DFSearch(g,p->num,s,path);
	}
	
	if (!found)		//如果該節點的所有鄰接點都不是目標結點，並且鄰接點的鄰接點也不是目標結點，那麼他就不是路徑上的，退出路徑 
	{
		path[--rear] = '\0';
	}
}

void path_algraph(algraph &g,char ch1,char ch2,char path[])		//求兩點之間的一般路徑 
{
	int i = locatenode(g,ch1);
	int s = locatenode(g,ch2);
	
	DFSearch(g,i,s,path);
}

int main(void)
{
	algraph g;
	init_algraph(g);
	creat_algraph(g);
	print_algraph(g);
//	DFStraverse(g,0);
	
	char ch1,ch2;
	scanf (" %c %c",&ch1,&ch2);
	char *path;
	path = (char *)malloc(sizeof(char)*MAX);
	
	path_algraph(g,ch1,ch2,path);
	
	int i=0;
	while(path[i])			//輸出路徑 
		printf ("%c ",path[i++]);
	
	return 0;
}