有人能帮我找下bug吗，我真的改不对了，看了一天了

Question

#include <stdio.h>
struct space create();
void print(struct space *p);
struct space mul(struct space *p1,struct space *p2);
struct space add(struct space *p1,struct space *p2);
void attach(int c,int e,struct space *L2);
    struct space{
        int xishu;
        int zhishu;
        struct space *next;
    };
int main(){
    struct space p1;
    struct space p2;
    struct space p3;
    struct space p4;
    p1 = create();
    p2 = create();
    p3 = mul(p1,p2);
    p4 = add(p1,p2);
    print(p3);
    print(p4);
    return 0;
}
struct space create(){ //创建链表 
    int n,i;
    scanf("%d",&n);
    struct space L,front;
    L=(struct space)malloc(sizeof(struct space));
    front=L;
    L=L->next;
    for(i=0;i<n;i++){
    L=(struct space)malloc(sizeof(struct space));
    scanf("%d %d",&L->xishu,&L->zhishu);
    L=L->next;
    }
    L->next=NULL;
    return front;
}
struct space mul(struct space *p1,struct space *p2){ //两个多项式相乘 
    struct space L,frontl,middle;
    L=(struct space)malloc(sizeof(struct space));
    L->next=NULL;
    frontl=L;
    p1=p1->next;
    p2=p2->next;
    middle1=p1;
    for(;middle1;middle1=middle1->next){
        middle2=p2;
        for(;middle2;middle2=middle2->next){
    L=(struct space)malloc(sizeof(struct space));
    L->xishu=(middle1->xishu)+(middle2->xishu);
    L->zhishu=(middle1->zhishu)*(middle2->zhishu);
    L=L->next;
        }
    }
    L->next = NULL;
    return front1;
}
struct space add(struct space p1,struct space p2){ //两个多项式相加 
    struct space L2,front2;
    L2=(struct space)malloc(sizeof(struct space));
    L2->next=NULL;
    front2=L2;
    p1=p1->next;
    p2=p2->next;
    while(p1&&p2){
    if(p1->zhishu>p2->zhishu){
        attach(p1->xishu,p1->zhishu,&L2);
        p1=p1->next;
    }else if(p2->zhishu>p2->zhishu){
        attach(p2->xishu,p2->zhishu,&L2);
        p2=p2->next;
    }else{
        if(p2->xishu+p1->xishu){
            ;
        }else{
            attach(p1->xishu+p2->xishu,p1->zhishu,&L2);
            p2=p2->next;
            p1=p1->next;
        }
    }
}
        L2->next=p1?p1:p2;
        return front2;
}
void attach(int c,int e,struct space *L2){ //将系数、指数插到新链表里 
    struct space p;
    p=(struct space)malloc(sizeof(struct space));
    p->xishu=c;
    p->zhishu=e;
    (*L2)->next=p;
    (*L2)=p;
}
void print(struct space *p){ //打印 
    p=p->next;
    while(p){
        printf("%d %d",p->xishu,p->zhishu);
        if(p->next){
        printf(" ");
        }
        p=p->next;
    }
}

Answer 1

其它问题我不知道。但是那个结构定义，都跟你说了，在哪里用到的前面就要有声明，听不听由你了。