求助，VC++程序问题！
/* Dijkstra.c

Copyright (c) 2002, 2006 by ctu_85
All Rights Reserved.
*/
#include "stdio.h "
#include "malloc.h "
#define maxium 32767
#define maxver 9 /*defines the max number of vertexs which the programm can handle*/
#define OK 1
struct Point
{
char vertex[3];
struct Link *work;
struct Point *next;
};
struct Link
{
char vertex[3];
int value;
struct Link *next;
};
struct Table /*the workbannch of the algorithm*/
{
int cost;
int Known;
char vertex[3];
char path[3];
struct Table *next;
};
int Dijkstra(struct Point *,struct Table *);
int PrintTable(int,struct Table *);
int PrintPath(int,struct Table *,struct Table *);
struct Table * CreateTable(int,int);
struct Point * FindSmallest(struct Table *,struct Point *);/*Find the vertex which has the smallest value reside in the table*/
int main()
{
int i,j,num,temp,val;
struct Point *poinpre,*poinhead,*poin;
struct Link *linpre,*lin;
struct Table *tabhead;
poinpre=poinhead=poin=(struct Point *)malloc(sizeof(struct Point));
poin-> next=NULL;
poin-> work=NULL;
restart:
printf( "Notice:if you wanna to input a vertex,you must use the format of number!\n ");
printf( "Please input the number of points:\n ");
scanf( "%d ",&num);
if(num> maxver||num <1||num%1!=0)
{
printf( "\nNumber of points exception! ");
goto restart;

}
for(i=0;i <num;i++)
{
printf( "Please input the points next to point %d,end with 0:\n ",i+1);
poin=(struct Point *)malloc(sizeof(struct Point));
poinpre-> next=poin;
poin-> vertex[0]= 'v ';
poin-> vertex[1]= '0 '+i+1;
poin-> vertex[2]= '\0 ';
linpre=lin=poin-> work;
linpre-> next=NULL;
for(j=0;j <num-1;j++)
{
printf( "The number of the %d th vertex linked to vertex %d: ",j+1,i+1);
scanf( "%d ",&temp);
if(temp==0)
{
lin-> next=NULL;
break;
}
else
{
lin=(struct Link *)malloc(sizeof(struct Link));
linpre-> next=lin;
lin-> vertex[0]= 'v ';
lin-> vertex[1]= '0 '+temp;

lin-> vertex[2]= '\0 ';
printf( "Please input the value betwixt %d th point towards %d th point: ",i+1,temp);
scanf( "%d ",&val);
lin-> value=val;
linpre=linpre-> next;
lin-> next=NULL;
}
}
poinpre=poinpre-> next;
poin-> next=NULL;
}
printf( "Please enter the vertex where Dijkstra algorithm starts:\n ");
scanf( "%d ",&temp);
tabhead=CreateTable(temp,num);
Dijkstra(poinhead,tabhead);
PrintTable(temp,tabhead);
return OK;
}
struct Table * CreateTable(int vertex,int total)
{
struct Table *head,*pre,*p;
int i;
head=pre=p=(struct Table *)malloc(sizeof(struct Table));
p-> next=NULL;
for(i=0;i <total;i++)
{
p=(struct Table *)malloc(sizeof(struct Table));
pre-> next=p;
if(i+1==vertex)
{
p-> vertex[0]= 'v ';

p-> vertex[1]= '0 '+i+1;
p-> vertex[2]= '\0 ';
p-> cost=0;
p-> Known=0;
}
else
{
p-> vertex[0]= 'v ';
p-> vertex[1]= '0 '+i+1;
p-> vertex[2]= '\0 ';
p-> cost=maxium;
p-> Known=0;
}
p-> next=NULL;
pre=pre-> next;
}
return head;
}
int Dijkstra(struct Point *p1,struct Table *p2) /* Core of the programm*/
{
char temp;
struct Point *poinhead=p1,*now;
struct Link *linna;
struct Table *tabhead=p2,*searc,*result;
while(1)
{
now=FindSmallest(tabhead,poinhead);
if(now==NULL)
break;
result=p2;
result=result-> next;

while(result!=NULL)
{
if(result-> vertex[1]==now-> vertex[1])
break;
else
result=result-> next;
}
linna=now-> work-> next;
while(linna!=NULL) /* update all the vertexs linked to the signed vertex*/
{
temp=linna-> vertex[1];
searc=tabhead-> next;
while(searc!=NULL)
{
if(searc-> vertex[1]==temp)/*find the vertex linked to the signed vertex in the table and update*/
{
if((result-> cost+linna-> value) <searc-> cost)
{
searc-> cost=result-> cost+linna-> value;/*set the new value*/

searc-> path[0]= 'v ';
searc-> path[1]=now-> vertex[1];
searc-> path[2]= '\0 ';
}
break;
}
else
searc=searc-> next;
}
linna=linna-> next;
}
}
return 1;
}
struct Point * FindSmallest(struct Table *head,struct Point *poinhead)
{
struct Point *result;
struct Table *temp;
int min=maxium,status=0;
head=head-> next;
poinhead=poinhead-> next;
while(head!=NULL)
{
if(!head-> Known&&head-> cost <min)
{
min=head-> cost;

result=poinhead;
temp=head;
status=1;
}
head=head-> next;
poinhead=poinhead-> next;
}
if(status)
{
temp-> Known=1;
return result;
}
else
return NULL;
}
int PrintTable(int start,struct Table *head)
{
struct Table *begin=head;
head=head-> next;
while(head!=NULL)
{
if((head-> vertex[1]- '0 ')!=start)
PrintPath(start,head,begin);
head=head-> next;
}
return OK;
}
int PrintPath(int start,struct Table *head,struct Table *begin)
{
struct Table *temp=begin-> next,*p,*t;
p=head;
t=begin;
if((p-> vertex[1]- '0 ')!=start&&p!=NULL)
{
while(temp-> vertex[1]!=p-> path[1]&&temp!=NULL)
temp=temp-> next;
PrintPath(start,temp,t);
printf( "%s ",p-> vertex);
}

else
if(p!=NULL)
printf( "\n%s ",p-> vertex);
return OK;
}
上面的程序可以运行，运行后界面可以输入第一个数据，但是输完以后就会报错，不能输入以后的数据，怎么回事，看不错来啊！帮我解决一下吧~！


[解决办法]
poin-> work=NULL;
;;;;;;;
linpre=lin=poin-> work;
linpre-> next=NULL;
linpre已经指向空了，怎么还能用空指向null？
[解决办法]
图论的基本算法
http://www.yuanma.org/data/2007/0205/article_2238.htm

先把算法看明白 ....