关于链表一元多项式求和的问题

Question

void Link:: Add(Node*L1,Node*L2)
{
Node*pre=L1,*p=pre->next;
Node*qre=L2,*q=qre->next,*v;
while(p!=NULL&&q!=NULL)
{
if(p->expexp)
{
pre=p;
p=p->next;
}
else if(p->exp>q->exp)
{
v=q->next;
pre->next=q;
q->next=p;
q=v;
pre=pre->next;
}
else
{
p->coef=q->coef+p->coef;
if(p->coef==0){
pre->next=p->next;
delete p;
p=pre->next;
}
else{
pre=p;
p=p->next;
}
qre->next=q->next;
delete q;
q=qre->next;
}
}
if(q!=NULL) p->next=q;
delete v;
delete qre;
delete L2;
qre=NULL;
L2=NULL;
}
这是我定义的加法函数（其中LInk类里的Nodefirst放到public里面了），可是运行的时候，会用访问位置冲突，希望大家可以帮忙看一下。（来自王红梅数据结构）

Answer 1

void Link:: Add(Node*L1,Node*L2)
{
Node*pre=L1,*p=pre->next;
Node*qre=L2,*q=qre->next,*v;
while(p!=NULL&&q!=NULL)
{
if(p->expexp)//这里应该是p->expexp
{
pre=p;
p=p->next;
}
else if(p->exp>q->exp)
{
v=q->next;
pre->next=q;
q->next=p;
q=v;
pre=pre->next;
}
else
{
p->coef=q->coef+p->coef;
if(p->coef==0){
pre->next=p->next;
delete p;
p=pre->next;
}
else{
pre=p;
p=p->next;
}
qre->next=q->next;
delete q;
q=qre->next;
}
}
if(q!=NULL) p->next=q;//报错的原因在这里，应该是if(q!=NULL) pre->next=q;
delete v;
delete qre;
delete L2;
qre=NULL;
L2=NULL;
}