我把你们指出的问题改了下，谢谢你们啊／
　特别是–★–,辛苦你了／
　改了这些问题后，又出现了一些毛病，经过我的努力还是能运行出正确的结果了，但还是有许多的不　　　　足，如：输入的多项式只能按指数从小到大的顺序，不是结果就不对了．．．．

修改后的程序如下：

#include<stdio.h>
#define NULL 0

typedef struct LNode
{
int coef;
int expn;
struct LNode *next;
} term;

typedef struct
{
term *head,*tail;
int len;
} LinkList;

void InitTerm(term *P)
{
P->next=NULL;
}

void InitList(LinkList *L)
{
L->head=L->tail=NULL;
L->len=0;
}

void CreatPolyn(term *P,LinkList *L,int m)
{
term *S,*T;int i;
InitList(L);InitTerm(P);
T=L->head=P;
T->coef=0;
T->expn=-1;
for(i=1; i<=m; ++i)
{
S=(term *)malloc(sizeof(term));
InitTerm(S);
scanf("%d %d",&S->coef,&S->expn);
T->next=S;
T=T->next;
}
L->tail=T;
L->len=m;
}

void AddPolyn(term *Pa,LinkList *La,term *Pb,LinkList *Lb)
{
term *ha,*hb,*qa,*qb;
int n;
float sum;
ha=La->head;
hb=Lb->head;
qa=Pa->next;qb=Pb->next;
while (qa && qb)
{
if(qa->expn>qb->expn)n=1;
else if(qa->expn<qb->expn)n=-1;
else n=0;
switch(n)
{
case -1: ha=qa;qa=qa->next;break;
case 0: sum=qa->coef+qb->coef;
if(sum!=0)
{ qa->coef=sum;
ha=qa;qa=qa->next;
hb=qb;qb=qb->next;
}
else
{ ha->next=qa->next;
qa=qa->next;
hb->next=qb->next;
qb=qb->next;
}
break;
case 1: hb=qb;
qb=qb->next;
ha->next=hb;
qb->next=qa;
hb=qb;
qb=qb->next;
break;
}
}
if(qb) ha->next=La->tail=qb;
free(Pb);
}

void PrintPolyn(term *P)
{
term *h;
h=P->next;
printf ("Y=");
while(h)
{
printf("%dx(%d)+",h->coef,h->expn);
h=h->next;
}
printf("\b \n");
}

void main()
{
term *Pa,*Pb;
LinkList *La,*Lb;
int n;
Pa=(term *)malloc(sizeof(term));
Pb=(term *)malloc(sizeof(term));
La=(LinkList *)malloc(sizeof(LinkList));
Lb=(LinkList *)malloc(sizeof(LinkList));
puts("Now,Creat the first polynomail:");
puts("\nplease input the numbers of the first polynomail: ");
scanf("%d",&n);
puts("\nPlease input coef and expn each term with order from small to large by expn:\n");
CreatPolyn(Pa,La,n);
puts("the first polynomail is:\n");
PrintPolyn(Pa);
puts("Now,Creat the second polynamail:\n");
puts("please input the numbers of the second polynamail:\n");
scanf("%d",&n);
puts("\nPlease input coef and expn each term with order from small to large yb expn:\n");
CreatPolyn(Pb,Lb,n);
puts("the second polynomail is:\n"); PrintPolyn(Pb);
AddPolyn(Pa,La,Pb,Lb);
puts("the result is:\n");
PrintPolyn(Pa);
}　　　　　　　　　　　　　　

有谁帮帮我啥 /
上面的那个出错信息是怎么回事/

TC自己的问题。具体看精华帖里（为什么一闪而过）

有三种解决办法，这里说一种,在主函数中加 float c,*p;p=&c;