为什么我的程序编译链接都没有错，得出来的结果却是零，而且还有一个NULL pointer assignment，大神帮帮忙

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#define NULL 0
typedef struct{
   int coaf;
   int expn;
}polym;
typedef struct LNode
{
    polym data;
    struct LNode *next;
}Node,*sqlist;
void  inistlist(sqlist *a,int n)
{
      a=(sqlist*)malloc(n*sizeof(polym)) ;
      printf("Please input the 0 Node:");
      scanf("%d%d",(*a)->data.coaf,(*a)->data.expn);
      (*a)->next=NULL;
}
void creatlist(sqlist *a,int n)
{
     int i;
     Node *p=NULL;
     inistlist(a,n);
     for(i=1;i<n;i++)
     {
       printf("Please input the %d Node:",i);
       scanf("%d%d",&p->data.coaf,&p->data.expn);
       (*a)->next=p;
     }
      p->next=NULL;
}
double sumarr(sqlist *a,int x)
{
       int i;
       double sum=0,temp;
       while((*a)->next!=NULL)
       {
            temp=pow(x,(*a)->data.expn);
            sum+= (*a)->data.coaf*temp;
            *a=(*a)->next;
       }
       return sum;
}
int main()
{
    sqlist *a=NULL;
    int n,x;
    double sum;
    printf("Please input the n,x:");
    scanf("%d%d",&n,&x);
    creatlist(a,n);
    sum=sumarr(a,x);
    printf("Sum=%f\n",sum);
    return 0;
}