编译没问题，但运行不了。。。。
#include<stdio.h>
typedef struct node
{
    float coef;
    int exp;
    struct node*next;}Pnode;
Pnode*createht(int tag)
{
    float x;int y;
    Pnode*p,*r,*h=(Pnode*)malloc(sizeof(Pnode));
    r=h;
    printf("input x,y:");
    scanf("%f%d",&x,&y);
    while(y!=tag)
    {
        p=(Pnode*)malloc(sizeof(Pnode));
        p->coef=x;
        p->exp=y;
        r->next=p;
        r=p;
        scanf("%f%d",&x,&y);
    }
    r->next =NULL;
    return h;
}
void poly(Pnode*h)
{
    Pnode*pre,*p,*q;
    pre=h;
    p=h->next;
    while(p)
    {
        if(p->exp==0)
        {
            pre->next =NULL;
            free(p);
            break;
        }
        else
        {
            p->coef =p->coef*p->exp ;
            p->exp --;
            pre=p->next;
        }
    }
}
main()
{
    int tag=-1;Pnode*h,*p;
    h=createht(tag);
    poly(h);
    p=h->next;
    while(p)
    {
        printf("%f%d\n",p->coef,p->exp);
        p=p->next ;
    }
}

谢了，if语句不用改，只改else语句就行啦，降序和升序是一样的 ，都能实现....