疑惑，可以帮我分析一下为什么会这样？
写了一个简单的动态链表，但是在执行的时候虽然提示输入第二个多项式，但实际上相当于无效输入，根本不显示多项式二的数据，如图：
程序代码：#include <stdio.h>
#include <stdlib.h>
typedef struct ploy {
double coef;
int expn;
struct ploy *next;
}Linklist;
int n = 0;
Linklist *creat()
{
Linklist *head, *p1, *p2;
p1 = p2 = (Linklist *)malloc(sizeof(Linklist *));
head = NULL;
scanf("%lf %d", &p1->coef, &p1->expn);
while (p1->coef != 0)
{
n++;
if (n == 1) head = p1;
else p2->next = p1;
p2 = p1;
p1 = (Linklist *)malloc(sizeof(Linklist *));
scanf("%lf %d", &p1->coef, &p1->expn);
}
p2->next = NULL;
return head;
}
void visit(Linklist *temp)
{
Linklist *ploy;
int i = 0;
ploy = temp;
while (ploy)
{
if (i == 0)
{
printf("%3.2lf*X^%d", ploy->coef, ploy->expn);
ploy = ploy->next;
i = 1;
}
else if (ploy->coef<0)
{
printf("%3.2lf*X^%d", ploy->coef, ploy->expn);
ploy = ploy->next;
}
else if (ploy->coef>0)
{
printf("+%3.2lf*X^%d", ploy->coef, ploy->expn);
ploy = ploy->next;
}
}
}
Linklist *sum(Linklist *ploy1, Linklist *ploy2)
{
Linklist *ptr1, *ptr2, *temp, *head;
temp = (Linklist *)malloc(sizeof(Linklist *));
head = ptr1 = ploy1;
ptr2 = ploy2;
while (ptr1 != NULL&&ptr2 !=NULL)
{
if (ptr1->expn == ptr2->expn)
{
ptr1->coef = ptr1->coef + ptr2->coef;
ptr1 = ptr1->next;
ptr2 = ptr2->next;
}
else if (ptr1->expn < ptr2->expn)
{
ptr1 = ptr1->next;
}
else if (ptr1->expn > ptr2->expn)
{
temp->coef = ptr2->coef;
temp->expn = ptr2->expn;
temp->next = ptr1->next;
ptr1->next = temp;
ptr2 = ptr2->next;
}
}
return head;
}
int main()
{
Linklist *L, *H, *result;
printf("输入多项式一：\n");
L = creat();
printf("输入多项式二：\n");
H = creat();
printf("输入的数据为：\n");
visit(L); visit(H);
result = sum (L, H);
printf("结果：\n");
visit(result);
printf("\n");
return 0;
}
