求大神解决一小问题！明早课题答辩突然发现的小毛病！在线等。急求！
在进行多项式相加减时，项数出了问题，始终为0.我输出的先是多项式的项数 然后是整个多项式#include<stdio.h>
#include<malloc.h>
typedef struct Polynomial{
float coef; //系数
int expn; //指数
struct Polynomial *next;
}*Polyn,Polynomial; //Polyn为结点指针类型
void Insert(Polyn p,Polyn h){
if(p->coef==0) free(p); //系数为0的话释放结点
else{
Polyn q1,q2;
q1=h;q2=h->next;//h为头结点
while(q2&&p->expn<q2->expn){ //查找插入位置
q1=q2;
q2=q2->next;
}
if(q2&&p->expn==q2->expn){ //将指数相同相合并
q2->coef+=p->coef;
free(p);
if(!q2->coef){ //系数为0的话释放结点
q1->next=q2->next;
free(q2);
}
}
else{ //指数为新时将结点插入
p->next=q2;
q1->next=p;
}
}
}//Insert
Polyn CreatePolyn(Polyn head,int m){//建立一个头指针为head、项数为m的一元多项式
int i;
Polyn p;
p=head=(Polyn)malloc(sizeof(struct Polynomial));
head->next=NULL;//首先创立一元多项式应为空
for(i=0;i<m;i++){
p=(Polyn)malloc(sizeof(struct Polynomial));//建立新结点以接收数据
head->expn=m;
printf("请输入第%d项的系数与指数:",i+1);
scanf("%f %d",&p->coef,&p->expn);
getchar();
Insert(p,head); //调用Insert函数插入结点
}
return head;
}//CreatePolyn
void DestroyPolyn(Polyn p){//销毁多项式p
Polyn q1,q2;
q1=p->next;
q2=q1->next;
while(q1->next){
free(q1);
q1=q2;//指针后移
q2=q2->next;
}
}
void PrintPolyn(Polyn head){
Polyn q=head->next;
printf ("%d ",head->expn);//头指针的指数是多项式的项数
int flag=1;//项数计数器
if(!q) { //若多项式为空，输出0
putchar('0');
printf("\n");
return;
}
while (q){
if(q->coef>0&&flag!=1) putchar('+'); //系数大于0且不是第一项
if(q->coef!=1&&q->coef!=-1){//系数非1或-1的普通情况
printf("%g",q->coef);
if(q->expn==1) putchar('X');
else if(q->expn) printf("X^%d",q->expn);
}
else{
if(q->coef==1){
if(!q->expn) putchar('1');
else if(q->expn==1) putchar('X');
else printf("X^%d",q->expn);
}
if(q->coef==-1){
if(!q->expn) printf("-1");
else if(q->expn==1) printf("-X");
else printf("-X^%d",q->expn);
}
}
q=q->next;
flag++;
}//while
printf("\n");
}//PrintPolyn
int compare(Polyn a,Polyn b){
if(a&&b){
if(!b||a->expn>b->expn) return 1;
else if(!a||a->expn<b->expn) return -1;
else return 0;
}
else if(!a&&b) return -1;//a多项式已空，但b多项式非空
else return 1;//b多项式已空，但a多项式非空
}//compare
Polyn AddPolyn(Polyn pa,Polyn pb){//求解并建立多项式a+b，返回其头指针
Polyn qa=pa->next;
Polyn qb=pb->next;
Polyn headc,hc,qc;
hc=(Polyn)malloc(sizeof(struct Polynomial));//建立头结点
hc->next=NULL;
headc=hc;
while(qa||qb){
qc=(Polyn)malloc(sizeof(struct Polynomial));
switch(compare(qa,qb)){
case 1:
{
qc->coef=qa->coef;
qc->expn=qa->expn;
qa=qa->next;
break;
}
case 0:
{
qc->coef=qa->coef+qb->coef;
qc->expn=qa->expn;
qa=qa->next;
qb=qb->next;
break;
}
case -1:
{
qc->coef=qb->coef;
qc->expn=qb->expn;
qb=qb->next;
break;
}
}//switch
if(qc->coef!=0){
qc->next=hc->next;
hc->next=qc;
hc=qc;
}
else free(qc);//当相加系数为0时，释放该结点
}//while
return headc;
}//AddPolyn
Polyn SubtractPolyn(Polyn pa,Polyn pb){//求解并建立多项式a-b，返回其头指针
Polyn h=pb;
Polyn p=pb->next;
Polyn pd;
while(p){ //将pb的系数取反
p->coef*=-1;
p=p->next;
}
pd=AddPolyn(pa,h);
for(p=h->next;p;p=p->next) //恢复pb的系数
p->coef*=-1;
return pd;
}//SubtractPolyn
float ValuePolyn(Polyn head,float x){//输入x值，计算并返回多项式的值
Polyn p;
int i;
float sum=0,t;
for(p=head->next;p;p=p->next){
t=1;
for(i=p->expn;i!=0;){
if(i<0){t/=x;i++;}//指数小于0，进行除法
else{t*=x;i--;}//指数大于0，进行乘法
}
sum+=p->coef*t;
}
return sum;
}//ValuePolyn
int main(){
int m,n,flag=0;
float x;
Polyn pa=0,pb=0,pc,pd;//定义各式的头指针，pa与pb在使用前付初值NULL
printf("请输入a的项数:");
scanf("%d",&m);
pa=CreatePolyn(pa,m);//建立多项式a
printf("请输入b的项数:");
scanf("%d",&n);
pb=CreatePolyn(pb,n);//建立多项式b
//输出菜单
printf(" *******************************************************\n");
printf(" * 多项式操作程序 *\n");
printf(" * *\n");
printf(" * 1:输出多项式a和b 2:建立多项式a+b *\n");
printf(" * *\n");
printf(" * 3: 建立多项式a-b 4:计算多项式a在x处的值*\n");
printf(" * *\n");
printf(" * 5: 退出 *\n");
printf(" * *\n");
printf(" *******************************************************\n");
for(;;flag=0){
printf("执行操作");
scanf("%d",&flag);
if(flag==1){
printf("多项式a：");PrintPolyn(pa);
printf("多项式b：");PrintPolyn(pb);continue;
}
if(flag==2){
pc=AddPolyn(pa,pb);
printf("多项式a+b：");PrintPolyn(pc);
DestroyPolyn(pc);continue;
}
if(flag==3){
pd=SubtractPolyn(pa,pb);
printf("多项式a-b：");PrintPolyn(pd);
DestroyPolyn(pd);continue;
}
if(flag==4){
printf("输入x的值：x=");
scanf("%f",&x);
printf("多项式a的值%g\n",ValuePolyn(pa,x));continue;
}
if(flag==5) break;
if(flag<1||flag>5) printf("Error!!!\n");continue;
}//for
DestroyPolyn(pa);
DestroyPolyn(pb);
return 0;
}
