运行结果错误，大神帮帮忙，两个多项式相加

#include <stdio.h>
#include <stdlib.h>
typedef struct Node
{
    int coef;//系数
    int expn;//指数
    struct Node *next;
}LNode;                       //LNode为创建的多项式链表类型      
struct elem
{
    int coef;
    int expn;
}List[100],change;            //List[]构建链表,change用来交换List[]中的某两项。
LNode* create(int n)           
{
    LNode *head;                                    
    LNode *s,*L;              //*s表示新创建的空表，*L表示当前的链表，用来连接两空表
    L=s=NULL;
    head=(LNode *)malloc(sizeof(LNode));
    head->next=0;                 //定义空链表
    L=(LNode *)malloc(sizeof(LNode));
    n--;                                            
    L->coef=List[1].coef;          //复制
    L->expn=List[1].expn;
    head->next=L;
    int i=2;            
    while(n)
    {
        s=(LNode *)malloc(sizeof(LNode));
        L->next=s;
        s->coef=List[i].coef;
        s->expn=List[i].expn;
        L=s;
        n--;
        i++;
    }
    L->next=0;
    return head;
}
LNode* add(LNode *p1,LNode *p2)   //将多项式p1与p2相加，结果存在第三个链表中（第三个链表由该函数创建）
{  

 
    p1=p1->next;              
    p2=p2->next;
    LNode *head;              
    LNode *L,*s;
    head=(LNode *)malloc(sizeof(LNode));
    head->next=NULL;
    L=head;
    while(p1&&p2)            //遍历两表，根据情况判断表的长短是否相同，是否缺项多项，建立一个新的链表来存取内容
    {
        if(p1->expn > p2->expn)//比较指数大小，将指数和系数较小的存入新表
        {
            s=(LNode *)malloc(sizeof(LNode));
            L->next=s;
            s->coef=p2->coef;
            s->expn=p2->expn;
            L=s;
            p2=p2->next;
        }
        if(p1->expn < p2->expn)//比较指数大小，将指数和系数较小的存入新表
        {
            s=(LNode *)malloc(sizeof(LNode));
            L->next=s;
            s->coef=p1->coef;
            s->expn=p1->expn;
            L=s;
            p1=p1->next;
        }
        if(p1->expn == p2->expn)//相等可以直接相加
        {
            s=(LNode *)malloc(sizeof(LNode));
            L->next=s;
            s->coef=p1->coef + p2->coef;
            s->expn=p1->expn;
            L=s;
            p1=p1->next;
            p2=p2->next;
        }
    }
    while(p1)//p1有剩余
    {
            s=(LNode *)malloc(sizeof(LNode));
            L->next=s;
            s->coef=p1->coef;
            s->expn=p1->expn;
            L=s;
            p1=p1->next;
    }
    while(p2)//p2有剩余
    {
            s=(LNode *)malloc(sizeof(LNode));
            L->next=s;
            s->coef=p2->coef;
            s->expn=p2->expn;
            L=s;
            p2=p2->next;
    }
    L->next=NULL;
    return head;
}
void print(LNode *p1)     //输出表
{
    p1=p1->next;
    while(p1)
    {
        printf("%d %d\n",p1->coef,p1->expn);
        p1=p1->next;
    }
}
int main()
{
    int z=2;
    LNode *head2[2];     //head2[]为两多项式的头结点
    int n;
    while(z)                                       
    {
    printf("请输入项数\n");
    scanf("%d",&n);
    printf("请输入各项\n");
    int i=1;
    for(i=1;i<=n;i++)
    {
        scanf("%d%d",&List[i].coef,&List[i].expn);
    }
    i=1;
    int j=1;
    for(i;i<n;i++)                                    
    for(j=i+1;j<=n;j++)
    {
        if(List[j].expn<List[i].expn)    //将输入的指数按升序排列 ，排序算法
        {
            change.coef=List[i].coef;
            change.expn=List[i].expn;
            List[i].coef=List[j].coef;
            List[i].expn=List[j].expn;
            List[j].coef=change.coef;
            List[j].expn=change.expn;
        }
    }
    head2[z]=create(n);
    z--;
    }
    LNode *pp;
    pp=add(head2[1],head2[2]);
    printf("结果为：\n");
    print(pp);
    system("pause");
    return 0;
}