程序运行之后显示内存不能read。麻烦看下哪里出错了。
#include<stdlib.h>
#include<stdio.h>
#include<ctype.h>
#include<malloc.h>
#include<iostream.h>

typedef struct pnode{  
    float coef;      
    int   exp;         
    struct pnode *next;
    struct pnode *prior;
}polynode;
    polynode *add(polynode *pa,polynode *pb)
    {
        polynode *p,*q,*r,*s,*t;
        float x;
        p=pa->next;q=pb->next;
        s=pa;
        while((p!=pa)&&(q!=pb))
        {
        if(p->exp<q->exp){s=p;p=p->next;}
        if(p->exp>q->exp){r=q->next;q->next=p;s->next=q;s=q;q=r;}
        else{
            x=p->coef+q->coef;
            if(x!=0){p->coef=x;s=p;}
            else{s->next=p->next;free(p);}
            p=s->next;r=q;q=q->next;free(r);
            }
        }
        if(q!=pb)
        {t=q;
        while(t->next!=pb)t=t->next;
            s->next=q;
            t->next=pa;
        }
        return(pa);
    }

polynode * CreatPolyn(polynode *P,int m)
{  
  if(m <= 0) return NULL;
  polynode *h = P = (pnode*)malloc(sizeof(pnode)), *Q;
  P->coef = 0.0;
  int i;
  printf("输入%d个非零项\n",m);
  for (i = 1; i <= m; ++i)
    {  
        scanf("%f%d",&P->coef,&P->exp);
        if(P->coef)
        Q = P;
        P = P->next = (polynode*)malloc(sizeof(polynode));
    }
  Q->next = NULL;
  free(P);
  return h;
} // CreatPolyn


   
   



void PrintfPoly(polynode *P)
{
  polynode *q = P;
  if(!q) {
   putchar('0');
      return;
  }
  if(q->coef!=1)
    {
     printf("%g",q->coef);
     if(q->exp==1) putchar('X');
     else if(q->exp) printf("X^%d",q->exp);
     }
  else if(!q->exp) putchar('1');
      else if(q->exp==1) putchar('X');
            else printf("X^%d",q->exp);
  q = q->next;
  while (q)
  {
     if(q->coef > 0) putchar('+');
     if(q->coef!=1)
     {
        printf("%g",q->coef);
        if(q->exp==1) putchar('X');
        else if(q->exp) printf("X^%d",q->exp);
        }
  

     else if(!q->exp) putchar('1');
          else if(q->exp==1) putchar('X');
                else printf("X^%d",q->exp);
     q = q->next;
  }
}




void main(){
     polynode *P1 = (polynode*)malloc(sizeof(polynode));
     polynode *P2 = (polynode*)malloc(sizeof(polynode));
     polynode * CreatPolyn(polynode *P,int m);
     polynode *polyadd(polynode *pa,polynode *pb);
     void PrintfPoly(polynode *P);
     P1=CreatPolyn(P1,5);
     P2=CreatPolyn(P2,5);
     P1=add(P1,P2);
     PrintfPoly(P1);


}

我对指针引用就是不熟悉。能不能帮我看下