一直出现value 3221225477问题，求解答

Question

typedef struct PNode{
float coef;
int expn;
struct PNode *next;
}PNode,*Polyminal;

void CreatePolyn(Polyminal L){
L=(Polyminal)malloc(sizeof(PNode));
L->next=NULL;
int i;
int n;
printf("请输入共有多少项");
scanf("%d",&n);
for(i=1;i<=n;i++){
PNode *s;
s=(PNode*)malloc(sizeof(PNode));
printf("请输入多项式的系数和指数\n");
scanf("%lf %d",&s->coef,&s->expn);
PNode *p;
PNode *q;
p=L;
q=L->next;
while(q&&q->expn < s->expn){
p=q;
q=q->next;
}
s->next=q;
p->next=s;
}
}

void Add(Polyminal L1,Polyminal L2){
PNode *a,*a1,*b,*temp;
a1=L1;
b=L2->next;
a=a1->next;
while(a&&b){
if(b->expn>a->expn){
a1=a;
a=a->next;
}
else if(b->expn==a->expn){
a->coef=a->coef+b->coef;
if(a->coef==0){
a1->next=a->next;
free(a);
a=a1->next;
b=b->next;
}
else{
a1=a;
a=a->next;
b=b->next;
}
}
else if(b->expnexpn){
temp=(Polyminal)malloc(sizeof(PNode));
temp->coef=b->coef;
temp->expn=b->expn;
temp->next=a1->next;
a1->next=temp;
a1=a1->next;
b=b->next;
}
a1->next=b?b:a;
}

}

void Output(Polyminal P){
PNode l;
P=(PNode)malloc(sizeof(PNode));
P->next=NULL;
l=P->next;
while(l){
printf("coef:%d expn:&d \n",l->coef,l->expn);
l=l->next;
}
}

int main(){
Polyminal L1,L2;
CreatePolyn(L1);
CreatePolyn(L2);
Add(L1,L2);
Output(L1);
return 1;
}

Answer 1

create函数这样写是不行的，外部L1和L2还是空的。参数改为指针的指针，或者返回值也用节点指针类型。main里用L1=createPolyn(L1);