#include<stdio.h>
#include<stdlib.h>
#include<string.h>
typedef struct node
{
        char ch;
        struct node*next;
        }linklist;
struct Stack
{
       char elements[100];
       int Top;
       };
linklist*head,*p,*q,*r;
Stack*S;
int n;
linklist*CREATLISTR();
void DELETE(linklist*p,linklist*head);
struct Stack*PUSHS(struct Stack*S,char E);
char POPS(struct Stack*S);

int main(void)
{
     int i,k;
     char ch2;
     S = NULL;
     printf("Enter n:\n");
     scanf("%d",&n);
     printf("Enter %d characters:\n",n);
     if(n>0)
     {
            head = CREATLISTR();
            p = head->next;
            for(k=1;k<=n/2;k++)
            {
                S = PUSHS(S,p->ch);
                r = p;
                p = p->next;
                DELETE(r,head);
                                }
            if(n%2!=0)
            {
                q = head->next;
                DELETE(q,head);
                }
            q = head->next;
            k = 0;
            for(i=1;i<=n/2;i++)
            {
                ch2 = POPS(S);
                if(q->ch!=ch2)
                {
                   printf("字符不对称!\n");
                   k++;
                   break;
                   }
                p = p->next;
                    }
            if(k==0)
               printf("字符对称！\n");           
            }
     else printf("Error!\n");
}
     
linklist*CREATLISTR()
{
       char ch3;
       int t=0;
       linklist*head ,*s,*r;
       head=(linklist*)malloc(sizeof(linklist)); /*生成头结点head*/
       r=head; /*尾指针指向头结点*/
       for(t=0;t<n;t++)
       {
            ch3=getchar();
            s=(linklist*)malloc(sizeof(linklist)); /*给新结点分配空间*/
            s->ch=ch3; r->next=s; /*新结点插入表尾*/
            r=s; /*尾指针r指向新的表尾*/
        }
        r->next=NULL;
        return head; /*返回表头指针*/
}

void DELETE(linklist*p,linklist*head)
{
       linklist*q;
       q=head;
       while(q->next!=p)
           q=q->next; /*查找*p的前趋结点*q*/
       q->next=p->next; /*删除结点*p*/
       free(p);
       }

struct Stack*PUSHS(struct Stack*S,char E)
{
       S->Top++;
       S->elements[S->Top]=E;
       return(S);
       }
      
char POPS(struct Stack*S)
{
       char temp;
       S->Top--;
       temp=S->elements[S->Top+1];
       return(temp);
       }

首先，main里面scanf("%d",&n);后面加上getchar();目的是清除缓冲区
其次，栈S并未分配内存，没有初始化，元素Top没有赋值就自增，错误。
将main中第三句S=NULL改为：

S=(Stack *)malloc(sizeof(Stack));
S->Top=0;

路过