C 试图实现Dijkstra,但存在毫无意义的分段错误
在函数Dijkstra中,我初始化了一个优先级队列nperm,它有一个info字段;这表明一个节点是否为集合notpermanent的成员。然后我有一个“I”字段,它实际存储指向该图形节点的指针(数组索引)和下一个指针。最初每个节点都是notpermanent集合的成员。初始化过程如下:C 试图实现Dijkstra,但存在毫无意义的分段错误,c,linked-list,segmentation-fault,dijkstra,C,Linked List,Segmentation Fault,Dijkstra,在函数Dijkstra中,我初始化了一个优先级队列nperm,它有一个info字段;这表明一个节点是否为集合notpermanent的成员。然后我有一个“I”字段,它实际存储指向该图形节点的指针(数组索引)和下一个指针。最初每个节点都是notpermanent集合的成员。初始化过程如下: for (i = graph; hnode[i].next >= 0;) { insertnperm(&nperm, 1, i); distance[i] = 500000;
for (i = graph; hnode[i].next >= 0;)
{
insertnperm(&nperm, 1, i);
distance[i] = 500000;
i = hnode[i].next;
}
距离[i]基本上是节点i与到目前为止已知的根节点之间的距离,因此,随着算法的进行,距离会更新,优先级队列nperm的顺序也会更新,这是基于距离的。
现在按照函数顺序,我传递一个指向优先级队列指针的指针,并将该指针的值存储在另一个相同类型的变量中,notperm p;p=*pq代码>,因为优先级队列中的每个节点都有一个字段“i”,其中包含图形节点的索引,所以我将列表遍历到距离最近更新的节点,并移除该节点,并将其放置在提升优先级队列中的适当位置
我使用语句while((p->I)!=s)
遍历到节点,但是出现了一个分段错误,对此我一无所知。当我使用p->i
访问“i”时,似乎出现了分段错误
谁能解释一下为什么会发生这种情况
这是完整的代码:
#include<stdio.h>
#include<conio.h>
#define MAXNODES 50
struct header
{
int info;
int epoint;
int tpoint;
int next;
};
struct header hnode[MAXNODES];
int i = 0;
struct arcs
{
int info;
int epoint;
int tpoint;
int enext;
int tnext;
};
int j = 0;
struct arcs anode[MAXNODES];
struct node
{
int info;
int i;
struct node *next;
};
typedef struct node *notperm;
notperm npgetnode(void)
{
notperm p;
p = (notperm) (malloc(sizeof(struct node)));
return p;
}
int hgetnode()
{
int k;
k = i++;
return k;
}
int agetnode()
{
int k;
k = j++;
return k;
}
void hfreenode(int r)
{
--i;
}
void afreenode(int r)
{
--j;
}
int addnode(int *pgraph, int x)
{
int p;
p = hgetnode();
hnode[p].info = x;
hnode[p].epoint = -1;
hnode[p].tpoint = -1;
hnode[p].next = *pgraph;
*pgraph = p;
return p;
}
void joinwt(int p, int q, int wt)
{
int r, r2;
int t, t2;
r2 = -1;
r = hnode[p].epoint;
while (r >= 0 && anode[r].epoint != q)
{
r2 = r;
r = anode[r].enext;
}
if (r >= 0)
{
anode[r].info = wt;
}
if (r < 0)
{
r = agetnode();
anode[r].epoint = q;
anode[r].tpoint = -1;
anode[r].enext = -1;
anode[r].tnext = -1;
anode[r].info = wt;
(r2 < 0) ? (hnode[p].epoint = r) : (anode[r2].enext = r);
}
/*updation to q */
t = hnode[q].tpoint;
t2 = -1;
while (t >= 0 && anode[r].tpoint != p)
{
t2 = t;
t = anode[t].tnext;
}
if (t >= 0)
{
anode[t].info = wt;
}
if (t < 0)
{
t = agetnode();
anode[t].tpoint = p;
anode[t].epoint = -1;
anode[t].tnext = -1;
anode[t].enext = -1;
anode[t].info = wt;
(t2 < 0) ? (hnode[q].tpoint = t) : (anode[t2].tnext = t);
}
}
void insertnperm(notperm * pq, int x, int currep)
{
notperm p;
if (*pq == NULL)
{
*pq = (notperm) (malloc(sizeof(struct node)));
(*pq)->info = x;
(*pq)->i = currep;
(*pq)->next = NULL;
return;
}
p = npgetnode();
p->info = x;
p->i = currep;
p->next = (*pq);
*pq = p;
}
void order(notperm * pq, int s, int distance[])
{
notperm p, q, j;
q = NULL;
p = NULL;
p = *pq;
while ((p->i/*this statement always ends up with a segmentation fault*/) != s)
{
q = p;
p = p->next;
}
if (q == NULL)
*pq = p->next;
else
q->next = p->next;
q = NULL;
for (j = *pq; distance[(j->i)] < distance[(p->i)]; j = j->next)
q = j;
if (q == NULL) {
p->next = *pq;
*pq = p;
}
else
{
p->next = q->next;
q->next = p;
}
}
void chngstozero(notperm * pq, int s)
{
notperm p;
for (p = *pq; (p->i) != s; p = p->next);
p->info = 0;
}
int checkstat(notperm * pq, int s)
{
notperm p;
for (p = *pq; (p->i) != s; p = p->next);
return (p->info);
}
int newminel(notperm * pq)
{
notperm p;
for (p = *pq; (p->info) != 1; p = p->next);
p->info = 0;
return (p->i);
}
void Dijkstra(int graph, int s, int t, int *pd)
{
unsigned int distance[MAXNODES], precede[MAXNODES];
int current, i, k, dc, currep;
unsigned int smalldist, newdist;
notperm p;
notperm nperm;
nperm = NULL;
for (i = graph; hnode[i].next >= 0;)
{
insertnperm(&nperm, 1, i);
distance[i] = 500000;
i = hnode[i].next;
}
distance[s] =0;
order(&nperm, s, distance);
chngstozero(&nperm, s);
current = s;
while (current != t)
{
smalldist = 500000;
dc = distance[current];
for (currep = hnode[current].epoint; anode[currep].enext >= 0; currep = anode[currep].enext)
{
if (checkstat(&nperm, currep))
{
newdist = dc + anode[currep].info;
if (newdist < distance[currep])
{
distance[currep] = newdist;
order(&nperm, currep, distance);
precede[currep] = current;
}
}
}
main()
{
int graph,a,b,c,d,e,wt,r,t,pd;
graph=-1;
int wt1=5;
int wt2=3;
int wt3=6;
int wt4=2;
int wt5=7;
a=addnode(&graph,4);
b=addnode(&graph,6);
c=addnode(&graph,8);
d=addnode(&graph,9);
e=addnode(&graph,5);
joinwt(a,b,wt);
joinwt(a,c,wt1);
joinwt(a,d,wt2);
joinwt(a,e,wt3);
joinwt(d,b,wt4);
joinwt(c,e,wt5);
Dijkstra(graph,a,e,&pd);
printf("%d",pd);
getch();
return 0;
}
#包括
#包括
#定义最大节点50
结构头
{
国际信息;
点-点;
内点;
int-next;
};
结构头hnode[MAXNODES];
int i=0;
结构弧
{
国际信息;
点-点;
内点;
int-enext;
int tnext;
};
int j=0;
结构弧阳极[MAXNODES];
结构节点
{
国际信息;
int i;
结构节点*下一步;
};
typedef结构节点*notperm;
notperm npgetnode(无效)
{
诺珀姆p;
p=(notperm)(malloc(sizeof(struct node));
返回p;
}
int hgetnode()
{
int k;
k=i++;
返回k;
}
int agetnode()
{
int k;
k=j++;
返回k;
}
void hfreenode(int r)
{
--一,;
}
void afreenode(int r)
{
--j;
}
int addnode(int*pgraph,int x)
{
INTP;
p=hgetnode();
hnode[p].info=x;
hnode[p].epoint=-1;
hnode[p].tpoint=-1;
hnode[p].next=*pgraph;
*pgraph=p;
返回p;
}
void joinwt(int p,int q,int wt)
{
int r,r2;
int t,t2;
r2=-1;
r=hnode[p].epoint;
while(r>=0&&阳极[r].epoint!=q)
{
r2=r;
r=阳极[r].enext;
}
如果(r>=0)
{
阳极[r].info=wt;
}
if(r<0)
{
r=agetnode();
阳极[r].epoint=q;
阳极[r].t点=-1;
阳极[r].enext=-1;
阳极[r].tnext=-1;
阳极[r].info=wt;
(r2<0)?(hnode[p].epoint=r):(阳极[r2].enext=r);
}
/*更新到q*/
t=hnode[q].t点;
t2=-1;
而(t>=0&&r.t点!=p)
{
t2=t;
t=阳极[t].t下一步;
}
如果(t>=0)
{
阳极[t].info=wt;
}
if(t<0)
{
t=agetnode();
阳极[t].t点=p;
阳极[t].epoint=-1;
阳极[t].tnext=-1;
阳极[t].enext=-1;
阳极[t].info=wt;
(t2<0)?(hnode[q].tpoint=t):(阳极[t2].tnext=t);
}
}
无效插入项(notperm*pq、int x、int currep)
{
诺珀姆p;
如果(*pq==NULL)
{
*pq=(notperm)(malloc(sizeof(struct node));
(*pq)->info=x;
(*pq)->i=电流;
(*pq)->next=NULL;
返回;
}
p=npgetnode();
p->info=x;
p->i=电流;
p->next=(*pq);
*pq=p;
}
无效顺序(notperm*pq,整数s,整数距离[])
{
非perm p,q,j;
q=零;
p=零;
p=*pq;
而((p->i/*此语句总是以分段错误结束*/)!=s)
{
q=p;
p=p->next;
}
if(q==NULL)
*pq=p->next;
其他的
q->next=p->next;
q=零;
对于(j=*pq;距离[(j->i)]i)];j=j->next)
q=j;
如果(q==NULL){
p->next=*pq;
*pq=p;
}
其他的
{
p->next=q->next;
q->next=p;
}
}
void chngstozero(notperm*pq,int s)
{
诺珀姆p;
对于(p=*pq;(p->i)!=s;p=p->next);
p->info=0;
}
int checkstat(notperm*pq,int s)
{
诺珀姆p;
对于(p=*pq;(p->i)!=s;p=p->next);
返回(p->info);
}
int newminel(非永久性*pq)
{
诺珀姆p;
对于(p=*pq;(p->info)!=1;p=p->next);
p->info=0;
返回(p->i);
}
void Dijkstra(int图,int s,int t,int*pd)
{
无符号整数距离[MAXNODES],在[MAXNODES]之前;
int电流,i,k,dc,currep;
无符号整数smalldist,newdist;
诺珀姆p;
非永久性nperm;
nperm=NULL;
对于(i=graph;hnode[i]。下一步>=0;)
{
插入nperm(&nperm,1,i);
距离[i]=500000;
i=hnode[i]。下一步;
}
距离[s]=0;
订单(nperm、s、距离(&N);
chngstozero&nperm,s;
电流=s;
while(当前!=t)
{
while ((p->i/*this statement always ends up with a segmentation fault*/) != s) {
q = p;
p = p->next;
}